Acoustic transponder, use of acoustic transponder, method for producing transponder, and acoustic transmission system

Abstract

To provide an acoustic transponder having a miniaturized structure.SOLUTION: An acoustic transponder 1 for an acoustic transmission system has: a transponder chip 2; and a piezoelectric element 4 for converting a carrier frequency into an electric voltage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an acoustic transponder for transmitting information by means of acoustic waves. The invention further relates to the use of an acoustic transponder and to a method for manufacturing an acoustic transponder. The invention further relates to a transmission system according to the above, which operates on acoustic waves. [Background technology]

[0002] Particularly in automated manufacturing processes, there is a need to identify tools made of metal. This can be used to know for each individual tool the manufacturer, the date of manufacture, the hours of use, the usable service life, or possibly the maintenance required (sharpening, refitting, etc.), and of course to enable allocation to a manufacturer, a specific batch, etc., in the event of a defect. For new manufacturing processes, particularly in the field of additive processes (printing of metal parts), identification is an equally important topic, for example when assembling multiple printed parts.

[0003] The workpieces themselves can use RFID (Radio-Frequency Identification) to indicate to Industry 4.0-compliant manufacturing equipment which processes should be used and in what order.

[0004] In this case, if the surface of the workpiece is altered by processing, surface-mounted identification means become an obstacle. In addition to identification, the measurement and transfer of characteristics originating from the interior of the tool or print piece, such as temperature, mechanical force or vibration, can also be important.

[0005] A particular topic is the analysis of the internal structure and homogeneity of the corresponding tool or printed part, which can be measured by sound waves reflected from manufacturing defects. The embedding of such a miniaturized measurement system, where the necessary drive power is transmitted and bidirectional communication exists, is likewise one possible application of the techniques described here.

[0006] There are several techniques for identification that could in principle be used, including optical barcodes or 2D codes, which can be printed on the surface, even in relief, line-based RFID processes, or well-documented handling of the tool.

[0007] All of these methods known today have drawbacks: it is difficult to attach antennas for radio-based processes directly to metal, and completely embedding them in metal is not possible in a physically meaningful way for the application, since electric and magnetic fields are practically completely absorbed by metal (Faraday cage). The use of ferrites for shielding, so-called glass transponders that can be embedded in blind holes in tools, is technically possible, but is expensive and prone to further problems, especially mechanical forces present in tools.

[0008] Some references to companies with RFID products working on this topic are listed in the Prior Art section.

[0009] Alternative ID technologies, such as labels, stickers and optical codes, which are also raised, are placed on the surface of the tool, where they are similarly at risk of becoming contaminated, illegible, etc. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] Internet (https: / / www.balluff.com / en / de / industries-and-solutions / solutions-and-technologies / tool-id / ) [Non-patent document 2] Internet (https: / / www.turck.de / en / tool-identification-480.php [Non-patent document 3] Internet (https: / / www.harting.com / UK / en-gb / markets / automatic-tool-identification) [Non-patent document 4] Internet (https: / / rfid-europe.com / product / anlagen-und-logistik-tag-confidex-ironside-micro / ) [Non-Patent Document 5] Internet (https: / / www.nfcwebshop.at / glass-tag-sokymat-hf-high-frequency-transponder.html) [Non-patent document 6] Internet (https: / / www.zoller.info / at / produkte / toolmanagement / datentransfer / zidcode?r=1) [Non-Patent Document 7] Internet (https: / / www.iis.fraunhofer.de / de / ff / lv / net / projekte / rfid_metall.html) [Non-patent document 8] Internet (https: / / www.harting.com / DE / de / rfid) [Non-Patent Document 9] Internet (https: / / www.innovating-automation.blog / tool-identification-in-metalworking-2 / ) Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to describe an acoustic transponder, the use of an acoustic transponder, a method for manufacturing an acoustic transponder and an acoustic transmission system that solve the above-mentioned problems. [Means for solving the problem]

[0012] This object is achieved by an acoustic transponder, by the use of a miniaturized transponder, by a method for producing a miniaturized transponder, and by an acoustic transmission system according to the independent claims.

[0013] According to one aspect, an acoustic transponder is described. The acoustic transponder is designed to enable information transmission by acoustic waves. The acoustic transponder is designed to be integrated into an acoustic transmission system. The acoustic transponder is characterized in that information processing, e.g., in the sense of receiving commands and replies with identification numbers, is performed entirely within the silicon chip and is not generated by, e.g., a reflector of acoustic surface waves (SAW (Surface Acoustic Wave) transponder).

[0014] Acoustic transponders are designed for the identification of objects (e.g., metal parts and / or 3D printed parts), for the control of objects, and / or for measurements inside objects. Acoustic transponders are designed for the acquisition of measurement data, for example, from the surface (internal or external) of an object and / or from inside the object. Acoustic transponders are designed to provide a communication channel for the transmission of information and energy by material waves, particularly through metal surfaces. Acoustic transponders are preferably designed for use in an extended temperature range of -40°C to +105°C.

[0015] The acoustic transponder comprises at least one, preferably exactly one, transponder chip. The transponder chip is a silicon chip. The transponder chip comprises an integrated circuit (IC - Integrated Circuit). The IC is preferably designed in a "bare die" structure (i.e. without a housing).

[0016] The acoustic transponder further comprises a piezoelectric element designed and arranged to convert a voltage signal, e.g., a carrier frequency, into an acoustic wave of the same signal type. The piezoelectric element is an electro-acoustic transducer. The piezoelectric element serves as a substrate for the acoustic transponder.

[0017] The piezoelectric element preferably comprises a lead-free material. Particularly preferably, the piezoelectric element consists of a lead-free material. The acoustic transponder is designed to be RoHS compliant (RoHS stands here for Restriction of (the use of certain) Hazardous Substances in Electrical and Electronic Equipment). Alternatively, the piezoelectric element may comprise, for example, PZT (Lead Zirconate Titanate).

[0018] The piezoelectric element is formed in the shape of a disk. In particular, the height or layer thickness of the piezoelectric element is smaller than the width or diameter of the piezoelectric element. Alternatively, the piezoelectric element may be formed in the shape of a rectangle. This is particularly practical when the transponder is to be coupled to a curved surface, such as a pipe wall. The acoustic transponder may accordingly be formed in the shape of a disk (cylindrical) or a rectangle. Due to its geometric shape and its material properties, the piezoelectric element exhibits resonance.

[0019] The acoustic transponder has a miniaturized structure. In other words, the acoustic transponder has a low overall height and / or a small volume. In particular, the acoustic transponder has a smaller or more compact design than conventional transponders for acoustic transmission systems. For example, the transponder has a height of <3 mm, e.g., ≦1 mm or ≦500 μm. The piezoelectric element has a height of ≦300 μm, preferably ≦200 μm.

[0020] Due to their miniaturized design, acoustic transponders can be installed very flexibly and can, for example, be completely embedded in an object. Instead of being integrated into an object, the transponders can be particularly easily adapted to a surface, for example an outer or inner surface, of an object. Acoustic transponders can also be particularly well adapted to the properties of existing systems, such as contactless cards or NFC (Near Field Communication) technology.

[0021] The information to be transmitted, contained in the mechanical vibrations, is then not subject to interference on the transmission channel by the electromagnetic fields of nearby systems, as is the case with radio-based methods.Acoustic identification methods using acoustic transponders can therefore be used even in the presence of strong electromagnetic fields.

[0022] Furthermore, because the transponder relies on the use of acoustic waves rather than electromagnetic waves, it does not require the same approval procedures and associated effort and costs for the use and sale of acoustic transponders.

[0023] According to one embodiment, the transponder is designed to be fully embedded within an object or workpiece. The workpiece may be a (preferably metallic) part and / or a 3D printed part. The workpiece may be a metal tool.

[0024] Due to the miniaturized structure, the transponder can be completely embedded in the workpiece. In particular, the surface of the workpiece can be completely closed in order to incorporate the acoustic transponder for identification therein. The entire surface of the workpiece can thereby be processed without impairing the identification of the workpiece.

[0025] The small overall height and small volume of the acoustic transponder result in little or negligible weakening of the workpiece (e.g., made of metal) in which the transponder is embedded. Furthermore, it is possible to embed the transponder in a small piece of metal. Due to the compact design of the transponder, its embedding does not create surface patterns and / or leave holes in the metal, as is the case for example with glass transponders. In particular, no externally recognizable defects are introduced, and no easily recognizable identification of the tagged object is introduced from the outside.

[0026] According to one embodiment, the transponder is designed to be acoustically coupled to the surface of a workpiece. The workpiece or object preferably comprises a metal. The workpiece may comprise a metal plate or a metal tube. In that case, the transponder may be removably (e.g., magnetically) or non-removably (e.g., with the aid of a thin adhesive layer) fixed to the metal surface. The transponder may be fixed to the inner or outer surface of the workpiece.

[0027] In order to achieve good acoustic contact between the transponder and the acoustic channel, i.e., the metal surface of the workpiece, a coating with a thin elastic layer can be provided on the underside of the transponder, in this context meaning the outer surface of the transponder that faces the workpiece in the assembled state.

[0028] The purpose of the coating is to fully fill the cavities formed due to the surface roughness of the opposing metal surfaces (the metal surface of the workpiece and the (metal) underside of the transponder) with a medium having a significantly higher acoustic impedance than air, thereby significantly increasing the efficiency of acoustic coupling.

[0029] According to one embodiment, the transponder chip is mounted onto the piezoelectric element using flip-chip technology.

[0030] The "direct chip attach" or "flip chip" technology for the connection between the transponder chip and the piezoelectric element allows the transponder structure to be kept very compact. The face of the transponder may correspond, for example, to the face of the bare die of the integrated circuit / transponder chip.

[0031] At typical feature sizes for 180nm chip manufacturing, the corresponding silicon die is approximately 0.4-4mm, depending on memory size and performance. 2 and a thickness of up to about 170 μm. The transponder chip may furthermore be embodied with so-called connection elements (for example bumps) which form protuberances on the surface and which provide contact connections to the piezoelectric elements.

[0032] Overall, a very small total height of, for example, about 500 μm (about 170 μm height of the transponder chip as bare die + about 300 μm height of the piezoelectric element as PCB (printed circuit board) + height of the protective cover or surface passivation) is obtained.

[0033] According to one embodiment, a circuit board is disposed between the transponder chip and the piezoelectric element, the circuit board establishing an electrical connection between the piezoelectric element and the transponder chip, where the transponder chip is preferably embodied as a packaged IC instead of a bare die.

[0034] The surfaces of the transponder or the piezoelectric element can correspond, for example, to the surfaces of a printed circuit board. The height of the circuit board is designed so that the overall height of the transponder is not excessively large. In particular, the circuit board is designed to be as thin as possible. Overall, a small combined height of approximately 3 mm at most is obtained.

[0035] The circuit board may have a relief structure on its underside, in which case the contact area between the circuit board and the piezoelectric element may be significantly reduced, so that only a small percentage of the surface of the circuit board is in contact with the piezoelectric element.

[0036] The circuit board allows additional electrical components, such as a matching network and / or sensors, to be easily connected to the piezoelectric element without the need for further connection means or process steps for connection, thus providing a particularly versatile and flexibly usable transponder.

[0037] According to one embodiment, the transponder chip is a Near Field Communication (NFC) chip.

[0038] The transponder chip preferably complies with the standards for use in the ISM frequency range of 13.56 MHz (proximity or proximity chips, also referred to as NFC chips). The NFC chip derives its system clock from the reader via the carrier frequency and can also operate in other frequency ranges, for example between 9 and 14 MHz. In this way, an optimal adaptation to the characteristics of the acoustic channel is possible. Overall, this provides a particularly flexible acoustic transponder.

[0039] According to one embodiment, the height or layer thickness of the piezoelectric material is set so that a thickness resonance, i.e. a steep drop in sound insulation, is formed in the range of 9 MHz to 14 MHz, in other words, the height of the piezoelectric material is selected so that the transponder is optimally usable in the frequency range of 9 MHz to 14 MHz.

[0040] In this way, the acoustic channel through the object obtains a "window of low attenuation", which can be advantageously used for energy and data transmission. The layer thickness or height of the piezoelectric material is preferably <300 μm, advantageously ≦200 μm.

[0041] According to one embodiment, the acoustic transponder comprises at least two electrodes. The electrodes are formed on at least the lower surface (lower electrode) and the upper surface (upper electrode) of the piezoelectric element. Preferably, a conductive material (electrode material) is also formed on at least one side surface of the piezoelectric element. This allows the electrodes to be led from the lower surface of the piezoelectric element through the side surface to the upper surface. This allows contact of the two electrodes from above.

[0042] The electrodes or conductive material preferably comprise silver, in particular silver solder paste. Preferably, the electrodes or conductive material are at least partially elastic. In particular, the electrodes have a greater elasticity than the connecting elements of the transponder chip.

[0043] The resilient configuration may prevent damage to the electrodes during manufacturing of the transponder, particularly during flip-chip assembly of the transponder chip onto the piezoelectric element.

[0044] One form of conductive electrode is further configured to ensure that the connecting elements (bumps and / or bonding wires) of the transponder chip are properly contacted with the piezoelectric element (and possibly a matching network, e.g., inductors). Preferably, the electrodes are further designed so that possible further components (e.g., intermediate elements and / or circuit boards) located between the transponder chip and the piezoelectric element can be easily and efficiently contacted.

[0045] Preferably, the electrodes are formed in a patterned manner, in particular on the upper surface (upper electrode) of the piezoelectric element, which may be patterned in the form of a layout to provide multiple parallel connection surfaces for, for example, inductors, transponder chips and / or further components.

[0046] The patterning of the top electrode can already be performed before the process of poling the piezoelectric element. In this way, part of the surface of the piezoelectric element can be kept free from electrically excited thickness vibrations during subsequent operation. Thus, by targeted patterning of the top electrode, the piezoelectric element can be divided into areas with stronger resonant thickness vibrations and areas that are not polarized and therefore remain quiet / non-vibrating.

[0047] The (parallel) capacitance of the piezoelectric element can likewise be tuned via the electrode geometry (and the dielectric properties of the piezoelectric material, eg PZT).

[0048] According to one embodiment, the electrical impedance between the piezoelectric element and the transponder chip is set by the structure of the piezoelectric element and / or the electrodes.

[0049] A piezoelectric element, through its opposing electrodes and the dielectric of the piezoelectric material between them, forms a capacitor. This results in a connection impedance at a specific frequency for a specific piezoelectric element, which is larger the smaller the capacitance. To avoid a matching network consisting of separate components, a well-matched connection impedance can be achieved, for example, by appropriate dimensioning of the electrodes. In particular, the material and / or height of the piezoelectric element and / or the material and / or size and / or patterning of the electrodes are selected to optimally set the impedance.

[0050] According to one embodiment, the acoustic transponder further comprises at least one component for electrical impedance matching. For example, the transponder may comprise an inductor. In this case, the inductor is a separate component (matching network) for impedance matching. The inductor may be formed as an SMD (Surface Mounted Device) component. The inductor may have a wire-wound structure or a ceramic multilayer structure. The inductor may be electrically connected to the piezoelectric element by reflow soldering. Alternatively, the inductor may be connected to the piezoelectric element by conductive adhesive.

[0051] An inductor is used in parallel with the capacitance of the piezoelectric element, and preferably the inductor is sized so that the imaginary part of the impedance cancels out at the operating frequency (over a wide range), as occurs in a resonant circuit.

[0052] According to one embodiment, the inductor is formed as a first planar coil. In other words, the inductor can be designed as a planar component. For example, the surface of the inductor corresponds to the surface of the piezoelectric element. In this case, the transponder can have an additional layer structure. In particular, an insulating layer can be formed between the inductor and the electrode on the upper surface of the piezoelectric element. The insulating layer can include a ferrite layer.

[0053] In conventional NFC technology, planar coils are used as loop antennas. The first planar coil acts as an emitter of an H-alternating magnetic field. This structure, which can eliminate the need for a transponder chip, creates a transparent transducer between the H-alternating magnetic field and sound waves.

[0054] The transducer can be glued onto a flat, smooth metal surface. In this case, the transducer converts NFC communication via the H alternating magnetic field in the air into material waves. A similar component glued opposite the metal surface will convert the material waves into the H alternating magnetic field (a passive relay for NFC signals through metal).

[0055] The transponder is designed as a resonant transducer, transparent between sound waves and an H-alternating magnetic field, by combining a thickness-oscillating piezoelectric element with a loop antenna in a laminated layer. Its use on a preferably metallic surface is facilitated by the use of a ferrite layer, which also provides electrical insulation. The layer used to bond the piezoelectric element to the metal surface, e.g., a thin epoxy resin adhesive layer, also contributes to the transmission characteristics of the acoustic channel.

[0056] The geometry of a material usually resonates in specific modes. For example, a metal plate exhibits narrowband resonances at multiples of the acoustic wavelength in the material, with strong damping between them, which manifest as resonant combs. However, piezoelectric elements also exhibit resonances due to their geometry and material properties as described above.

[0057] Due to the aforementioned elastic material properties of the adhesive layer, these modes can be superimposed to form an acoustic transmission channel with a relatively flat passband, lacking the strong attenuation of the resonant comb. Such a channel can be used for data transmission via NFC technology. Such a flat passband can be in a range greater than 10 MHz, for example, greater than 10.5 MHz. For example, the range can be around 11 MHz.

[0058] The dependence of this channel on temperature and thickness of the uniform metal material is very small, since the individual peaks and notches of the resonant comb are not as evident in the fully transparent communication window as they are outside this region.

[0059] The permeable resonant transducer may further include an inductively coupled second planar coil formed on the lower surface of the piezoelectric element. The second planar coil has a larger area than the first planar coil. The second planar coil may be disposed on a ferrite foil for magnetic insulation. Thus, the ferrite foil is between the lower electrode and the second planar coil.

[0060] The first planar coil can be extended to a larger antenna in the usual formats of ID cards (ID1 according to ISO / IEC 7810 or antenna classes 1 to 6 according to ISO / IEC 14443) by coupling it to a second planar coil. This allows the effective area of ​​the planar coil to be effectively adapted to the usual formats, such as the ID-1 card format, and to the antenna size of the NFC interface. This provides a particularly adaptable and flexibly usable transducer.

[0061] According to one embodiment, the acoustic transponder comprises at least one identification number and / or at least one sensor, preferably a MEMS (Micro Electromechanical System) sensor.

[0062] The identification number is used for secure authentication with the acoustic link. The miniaturization of the acoustic transponder can further be used for location determination simultaneously with identification and / or authentication. In particular, the miniaturized structure of the transponder can be optimally used to determine a relatively precise position of the transponder. This facilitates reading the transponder or identifying the workpiece in which the transponder is embedded. Thereby, a particularly efficient acoustic transponder is provided.

[0063] The sensor may be a temperature sensor, a pressure sensor, a humidity sensor, a gas sensor, a light sensor, a pulse counter, a microphone and / or similar types of sensors.

[0064] In particular, MEMS sensors can be manufactured cheaply in large quantities, have good electrical properties and good signal-to-noise ratios, and have low energy consumption, which can provide efficient and universally usable transponders.

[0065] According to one embodiment, a miniaturized acoustic transponder can be used as an input element in functions involving secure authentication. First, authentication allows access to input information. The determined position makes it possible to operate a display on the metal, for example. For this purpose, the input element / display can be attached (e.g., glued) to the surface of the workpiece in which the transponder is installed and / or to which the transponder is coupled. This provides a particularly flexible transponder for use.

[0066] According to one embodiment, the transponder comprises at least one protective element, which is designed and arranged to protect the acoustic transponder from external influences. The at least one protective element preferably comprises a casting compound (mold). The casting compound completely covers the top surface of the transponder. The casting compound may also cover part of the side surfaces of the transponder.

[0067] The casting compound may be transparent to allow the transponder to emit light. Alternatively, the casting compound may be opaque to prevent light from affecting the function of the transponder. The casting compound may further include magnetizable particles.

[0068] To prevent the casting compound from covering most of the surface of the piezoelectric element, a non-wettable structure / sphere can be used as an underlayer between the casting compound and the piezoelectric element. The circuit board mentioned above between the transponder chip and the piezoelectric element can also prevent the piezoelectric element from being wetted by the casting compound.

[0069] The at least one protective element may further include a rim that extends along the periphery of the transponder. The rim forms a kind of collar around the side of the transponder. The rim increases the height of the transponder. In other words, the height of the rim is greater than the height of the transponder before the rim is placed.

[0070] The volume of the inner area of ​​the rim is filled with the casting compound, the rim thus forms a reservoir or limited volume for the casting compound, and furthermore the rim protects the sides of the transponder from external influences.

[0071] The at least one protective element may further comprise a membrane. The membrane is formed on the underside of the transponder. However, the membrane may additionally extend at least partially over the side of the transponder. The membrane protects the underside of the transponder from external influences. The membrane may comprise steel. The membrane may have a larger area than the piezoelectric element. The lower end of the rim may rest on the membrane. The rim and the membrane may thereby form a kind of sleeve for the transponder.

[0072] The membrane can be made magnetic. Furthermore, the edge can also be made magnetic. In an acoustic transmission system with a magnetic counterpart on the primary side, the transponder and its counterpart can be aligned and / or fixed to each other.

[0073] According to one embodiment, the transponder further comprises an intermediate element (interposer), which is formed between the piezoelectric element and the transponder chip.

[0074] The intermediate element may have a metallized surface for establishing an electrical connection with the piezoelectric element and / or the transponder chip and / or other components of the transponder, such as for example an inductor.

[0075] Preferably, the metallized surface of the intermediate element is at least partially patterned, and in particular the lower surface of the intermediate element facing the piezoelectric element may have a structure for providing multiple parallel electrical contacts and / or for minimizing the contact area between the intermediate element and the piezoelectric element, thereby improving the reliability of the electrical connection.

[0076] For example, a short cylinder can protrude from the lower surface of the intermediate element. Alternatively, the lower surface can have a honeycomb, i.e., polygonal wall, structure. In this way, the intermediate element can mechanically contact only a small portion of the surface area of ​​the piezoelectric element (e.g., 10% of the surface area), while the remaining area can vibrate freely. The piezoelectric element is thereby less susceptible to thickness vibrations. Furthermore, the influence can be targeted and utilized by appropriately selecting the proportion of surface contact.

[0077] However, according to one embodiment, the intermediate element can also have a molded part. The molded part comprises plastic. The intermediate element is a 3D plastic molded part. The molded part comprises conductor tracks for electrical contact. The conductor tracks can extend on the outer surface of the intermediate element. Alternatively or additionally, the intermediate element can comprise conductor tracks located on the inside.

[0078] Preferably, the conductive paths are formed on the surface of the molded part. In particular, the intermediate element is manufactured by a method in which conductive paths can be formed on the surface by laser processing on a plastic molded part doped with approximately 4% metal particles.

[0079] According to one embodiment, the material and / or structure of the intermediate element is designed for vibration isolation or damping. Preferably, the intermediate element is designed to be elastic. Preferably, the intermediate element is configured elastically so that vibrations due to sound waves, in particular in the 13.56 MHz range, are well absorbed. This can be achieved through cooperation of the relief shape and the material properties. This provides a transponder that is very flexible in use and easily adjustable.

[0080] According to one embodiment, the intermediate element is designed in a thermally insulated manner, preferably comprising a material with very good thermal insulation properties, so that the temperature-sensitive electronics of the transponder can be efficiently protected against higher temperatures that may occur in the short term.

[0081] According to a further aspect, a use of a miniaturized transponder is described. The miniaturized transponder preferably corresponds to the transponder described above. All features disclosed with respect to the transponder or the use are correspondingly disclosed with respect to each other aspect, even if the respective feature is not explicitly mentioned in the context of the respective aspect, and vice versa. The transponder is used in an object, for example, a metal tool or a 3D printed object.

[0082] The transponder is completely embedded in the object. In particular, surface defects of the object cannot be recognized by the transponder. The transponder remains in the object for the object's lifetime. In other words, it is not intended to be removed from the object. The transponder remains in the object in order to acquire measurement data from inside the object and / or to identify and / or control the object.

[0083] Alternatively, the transponder is coupled to the surface of a metallic object, such as a metal plate or a metal pipe. The surface may be the outer and / or inner surface of the object. The transponder may be coupled to the surface removably or permanently. For example, the transponder is connected to the metal surface magnetically or with the aid of an adhesive. Preferably, the adhesive is elastic. The transponder is coupled to the surface of the object for object identification and / or for acquisition of measurement data and / or for object control.

[0084] For measurement data acquisition, the transponder may also be equipped with a connected sensor, such as a MEMS sensor. For identification, the transponder may further have an identification number. Preferably, the transponder may be used as an input element. For this purpose, a display may be attached to the surface of the object, through which the user can input data.

[0085] According to a further aspect, an acoustic transmission system is described. German patent application no. 102020108905.8, the contents of which are incorporated herein by reference, describes a corresponding acoustic transmission system and concept relating to the use of sound waves to transmit information for the purpose of identification of tools or 3D printed parts by their metallic material.

[0086] An acoustic transmission system has a primary side and a secondary side: on the primary side, the transmission system comprises a transmitting unit, a receiving unit (a so-called "reader") and an electro-acoustic transducer, for example a piezoelectric element.

[0087] The transmitting unit is intended and designed to provide a transmitted signal, the receiving unit is intended and designed to receive a received signal in response to the transmitted signal, and the electro-acoustic transducer is intended and designed to convert the transmitted signal into an acoustic signal and convert the acoustic signal into a received signal.

[0088] Furthermore, the acoustic transmission system includes a miniaturized transponder on the secondary side, which includes a transponder chip and an electro-acoustic transducer (piezoelectric element).

[0089] The miniaturized transponder corresponds to the miniaturized transponder described above. In particular, the miniaturized transponder has all the features described in relation to the transponder above. The miniaturized transponder is intended and designed to receive receive signals and transmit transmit signals. The transponder is designed and arranged to use the clock of the receiving unit as the system clock. The piezoelectric element of the miniaturized transponder on the secondary side can be in acoustic contact with the electro-acoustic transducer on the primary side.

[0090] The acoustic transmission system further includes an acoustic coupling medium between the primary side and the secondary side, the coupling medium being transparent to the acoustic signal, and may include gel or oil.

[0091] Acoustic transmission systems use sound waves to transmit information for the purpose of identifying objects, such as metal tools or 3D printed parts, and this principle is virtually independent of the surface of the object to be identified.

[0092] The surface can be, for example, completely closed and hold an acoustic identification tag inside. Furthermore, it is possible to process the entire surface of the object and still obtain identification. Alternatively, the transponder can be coupled to the surface of the object. To enable processing of the surface, the transponder can be removably connected to the surface. This provides a system for reliable and efficient information transmission that is independent of further processing of the object to be identified.

[0093] The particularly small (miniaturized) and easily embodied nature of the acoustic transponder allows it to be embedded in or coupled to small objects (tools, metal parts, metal plates, or metal tubes) without significantly weakening the structure. This miniaturization is also an advantage compared to loop antennas, which are used, for example, in the range of approximately 13.56 MHz and cannot be constructed as efficiently small as acoustic structures allow. This provides a particularly flexible system for information transmission. The miniaturization of the transponder further allows for very accurate position determination and therefore very efficient reading of the transponder.

[0094] According to one embodiment, the receiving unit is designed and arranged to control multiple piezoelectric elements, for example 2, 3, 5 or 10 piezoelectric elements, thereby creating a larger area for detecting multiple acoustic transponders. This can occur sequentially or in a time-sequenced manner in a multiplexed manner. In this way, a display for HMI (Human Machine Interface) input can also be built.

[0095] According to one embodiment, the receiving unit is designed and arranged to control a piezoelectric element that is larger than the piezoelectric element of the miniaturized transponder, thereby allowing for an increased detection area and / or multiple acoustic transponders to be required.

[0096] According to a further aspect, a method for manufacturing a miniaturized transponder is described. Preferably, the method manufactures the transponder described above. All features disclosed with respect to the transponder or the method are correspondingly disclosed with respect to each other aspect, and vice versa, even if the respective feature is not explicitly mentioned in the context of the respective aspect. The method comprises the following steps:

[0097] A) preparing a number of transponder chips having a number of integrated circuits on a wafer; each transponder chip can have at least one connection element, preferably two connection elements. The connection elements are preferably formed as bumps. The connection elements preferably comprise gold.

[0098] The transponder chips are preferably used as bare dies in miniaturized transponders, each having a maximum height of 170 μm.

[0099] B) Providing a number of piezoelectric elements. The piezoelectric elements are formed in the shape of a disk. Alternatively, the piezoelectric elements may be formed in the shape of a rectangle. The piezoelectric elements comprise, for example, homogeneous PZT. The piezoelectric elements have a maximum height of 300 μm, preferably 200 μm. Each piezoelectric element is an electro-acoustic transducer. Each piezoelectric element serves as a substrate for a miniaturized acoustic transponder.

[0100] An electrode is formed on each of the lower and upper surfaces of each piezoelectric element.

[0101] Preferably, the electrode material is also present on at least one side of the piezoelectric element. The electrodes comprise a material with elastic properties, for example silver. In particular, the material of the electrodes is more elastic than the material of the connecting element.

[0102] C) Step of preparing a connecting means, for example, an adhesive. The connecting means preferably includes an epoxy resin. The connecting means has elastic properties. If a circuit board is provided between the piezoelectric element and the transponder chip, this step can be omitted.

[0103] D) electrically and mechanically connecting the transponder chip and the piezoelectric element with the aid of connecting means; in particular, each piezoelectric element and each transponder chip are connected to one another by flip-chip assembly. This step can also be omitted if a circuit board is provided between the piezoelectric element and the transponder chip. Rather, in this step, the circuit board is connected to the piezoelectric element and the transponder chip, which here is preferably embodied as a packaged chip.

[0104] Additionally, at this point, a coating or surface passivation can be applied, which helps protect against corrosion and may also help isolate the top surface of the transponder from pressure and temperature.

[0105] E) Separation into individual components to produce a large number of miniaturized transponders.

[0106] In an optional further step, before the connection of the transponder chip and the piezoelectric element, the above-mentioned intermediate element can be prepared and placed on the piezoelectric element, after which the transponder chip is connected to the upper surface of the intermediate element with the help of connecting means.

[0107] The method, in the form of so-called wafer level packaging, allows for parallel processing and testing of a large number of units, thus enabling the efficient and cost-effective provision of a large number of miniaturized transponders.

[0108] The present disclosure includes, among other aspects, the following:

[0109] 1. An acoustic transponder (1) for an acoustic transmission system, comprising: a transponder chip (2); a piezoelectric element (4) for converting a carrier frequency into a voltage; The transponder (1) has a miniaturized structure.

[0110] 2. The acoustic transponder (1) according to aspect 1, The transponder (1) has a height of <3 mm.

[0111] 3. The acoustic transponder (1) according to aspect 1 or 2, The piezoelectric element (4) has a height of 300 μm or less.

[0112] 4. An acoustic transponder (1) according to any of the preceding aspects, The transponder (1) is configured to be completely embedded within the workpiece.

[0113] 5. The acoustic transponder (1) according to aspect 4, The workpiece is a metal part and / or a 3D printed part.

[0114] 6. The acoustic transponder (1) according to any of the preceding aspects, The transponder chip (2) is mounted on the piezoelectric element (4) by flip-chip technology.

[0115] 7. The acoustic transponder (1) according to any of the preceding aspects, The height of the piezoelectric material is adjusted so that a thickness mode resonance in the range of 9 MHz to 14 MHz is formed.

[0116] 8. The acoustic transponder (1) according to any of the preceding aspects, The piezoelectric element (4) further comprises at least two electrodes (5), the electrodes (5) being formed on at least the lower surface (4b) and the upper surface (4a) of the piezoelectric element (4), and the electrodes (5) being formed at least partially elastically.

[0117] 9. The acoustic transponder (1) according to any of the preceding aspects or aspect 8, The electrical impedance between the piezoelectric element (4) and the transponder chip (2) is adjusted by the structure of the piezoelectric element (4) and / or the electrode (5).

[0118] 10. The acoustic transponder (1) according to any of the preceding aspects, It further comprises at least one component for electrical impedance matching.

[0119] 11. The acoustic transponder (1) according to aspect 10, The transponder (1) includes an inductor for adjusting the impedance, and the inductor is connected in parallel to the capacitance of the piezoelectric element (4).

[0120] 12. The acoustic transponder (1) according to any of the preceding aspects, The transponder chip (2) is an NFC chip.

[0121] 13. An acoustic transponder (1) according to any of the preceding aspects, The device further comprises at least one MEMS sensor.

[0122] 14. An acoustic transponder (1) according to any of the preceding aspects, It also has an identification number for positive authentication.

[0123] 15. An acoustic transponder (1) according to any of the preceding aspects, The miniaturization of the acoustic transponder (1) allows it to be used for location determination and at the same time for identification and / or authentication.

[0124] 16. The acoustic transponder (1) according to any of the preceding aspects, The piezoelectric element (4) is made of lead-free material.

[0125] 17. Use of a miniaturized acoustic transponder (1) in an object (8), wherein the transponder (1) is completely embedded in the object (8) and the transponder (1) remains in the object (8) for the lifetime of the object (8) for the acquisition of measurement data from inside the object (8) and / or for the identification of the object (8) and / or for the control of the object (8).

[0126] 18. The use according to embodiment 17, The miniaturized acoustic transponder (1) can be used as an input element in functions involving secure authentication.

[0127] 19. An acoustic transmission system comprising: A) On the primary side: - a transmitting unit intended and suitable for providing a transmitting signal; a receiving unit intended and suitable for receiving a received signal in response to said transmitted signal; - an electro-acoustic transducer intended and suitable for converting said transmission signals into acoustic signals and acoustic signals into reception signals, B) Secondary side: A miniaturized transponder (1) according to any one of aspects 1 to 16, comprising a transponder (1) intended and suitable for receiving incoming signals and transmitting outgoing signals, C) An acoustic coupling medium is provided between the primary side and the secondary side.

[0128] 20. The acoustic transmission system according to aspect 19, The transponder (1) is designed and arranged to use the clock of the receiving unit as its system clock.

[0129] 21. The acoustic transmission system according to aspect 19 or 20, The receiving unit is designed to control multiple piezoelectric elements (4) and / or to control a piezoelectric element (4) that is larger than the transponder (1), thereby increasing the detection range and / or acting on multiple acoustic transponders (1).

[0130] 22. A method for manufacturing a miniaturized transponder (1) for an acoustic transmission system, comprising the following steps: A) preparing a number of transponder chips (2) having a number of integrated circuits on a wafer; B) preparing a number of piezoelectric elements (4), each of which has an electrode (5) formed on at least a lower surface (4b) and an upper surface (4a); C) providing a connecting means (6); D) electrically and mechanically connecting the transponder chip (2) and the piezoelectric element (4) with the aid of said connecting means (6); E) Separation into individual components to produce a large number of miniaturized transponders (1).

[0131] 23. The method according to embodiment 22, Each of the piezoelectric elements (4) and each of the transponder chips (2) are connected to each other by a flip-chip assembly.

[0132] 24. The method according to aspect 22 or 23, The method further includes the steps of: Applying a passivation, said passivation being applied prior to separation into individual components.

[0133] The drawings described below should not be construed as being to scale, rather individual dimensions may be shown enlarged, reduced or distorted for better illustration.

[0134] Components that are identical to one another or perform the same functions are designated by the same reference numerals. [Brief explanation of the drawings]

[0135] [Figure 1] 1A-1D are cross-sectional views of intermediate stages in the manufacture of a miniaturized transponder according to one embodiment. [Figure 2] 1 is a cross-sectional view of a miniaturized transponder according to one embodiment. [Figure 3] 1 is a cross-sectional view of a miniaturized transponder embedded within an object. [Figure 4] FIG. 10 is a cross-sectional view of a miniaturized transponder according to another embodiment. [Figure 5] FIG. 10 is a cross-sectional view of a miniaturized transponder according to another embodiment. [Figure 6] FIG. 10 is a cross-sectional view of a miniaturized transponder according to another embodiment. [Figure 7] FIG. 10 is a cross-sectional view of a miniaturized transponder according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0136] 2 shows an acoustic transponder 1, or transponder 1 for short, in a miniaturized construction. The transponder 1 allows information transmission by acoustic waves and is designed to be integrated into an acoustic transmission system (not shown) for this purpose.

[0137] The transponder 1 is used for the identification of an object 8 (see FIG. 3). The object 8 can be, for example, a metal part (e.g., a metal tool) or a 3D printed part. The transponder 1 can, for example, carry an identification number, thereby ensuring reliable authentication of the object 8.

[0138] The transponder 1 may further be used for controlling the object 8 (e.g. a battery) and / or for measurements inside the object 8. For the latter, the transponder 1 may be equipped with a sensor, e.g. a MEMS sensor (not explicitly shown).

[0139] The transponder 1 comprises a transponder chip 2. The transponder chip 2 comprises an integrated circuit. The transponder chip 2 functions as a bare die of the transponder 1. The transponder chip 2 is an NFC chip and therefore supports a frequency of substantially 13.56 MHz. The NFC transponder chip derives its system clock from the reader via the carrier frequency and can therefore also operate in a wider frequency range, for example, 9-14 MHz. The maximum height of the transponder chip 1 is 170 μm.

[0140] The transponder chip 2 comprises two connection elements 3, which are formed on the underside of the transponder chip 2. In this embodiment, the connection elements 3 are bumps. The connection elements 3 comprise a rigid material, preferably gold. The connection elements 3 are used to electrically connect the transponder chip 2 to the piezoelectric element 4.

[0141] The piezoelectric element 4 is used to convert a carrier frequency as a signal waveform of an acoustic wave into a signal waveform of a voltage. It is an electro-acoustic transducer. The piezoelectric element 4 can include PZT or a lead-free material and is formed in a disk shape.

[0142] The piezoelectric element 4 has a height of <300 μm, preferably ≦200 μm. In this context, the height of the piezoelectric element 4 is understood as the extent of the piezoelectric element 4 perpendicular to the main direction of extension of the transponder 1.

[0143] The piezoelectric element 4 functions as a circuit board for the transponder 1 and is provided with electrodes 5. The electrodes 5 are formed on at least the lower surface 4b (see FIG. 1) and the upper surface 4b of the piezoelectric element 4. The electrodes 5 may also extend along one or both side surfaces of the piezoelectric element 4 for electrical contact of both electrodes from the upper surface 4a. Therefore, it can be seen from FIG. 2 that a conductive material 7 (electrode material) covers the side surfaces of the piezoelectric element 4 to lead the lower electrodes 5 to the upper surface 4a.

[0144] The electrode 5 is patterned. In particular, the electrode 5 is formed over the entire bottom surface 4b. In contrast, the electrode 5 on the top surface 4a covers only a partial area of ​​the top surface 4a of the piezoelectric element 4.

[0145] It is crucial for the functioning of the transponder chip 2 that the carrier frequency coming from the reader and converted into a voltage via the piezoelectric element 4 has the correct voltage amplitude. Due to the IC input structure, e.g. pp A minimum voltage of 0.5mA is required. Furthermore, a certain minimum current is required, for example 0.5mA. If a higher voltage occurs, this is limited by a voltage limiter within the IC.

[0146] The piezoelectric element 4 represents a capacitor component. The transponder chip 2, as mentioned above, requires a specific voltage at its input, which in turn requires a specific capacitance of the piezoelectric element 4. For a specific piezoelectric element 4, a connection impedance is obtained at a specific frequency, which is higher the smaller the capacitance. To avoid a matching network consisting of separate components (e.g., inductors), a well-matched connection impedance can be achieved by appropriately dimensioning and / or patterning the electrodes 5 (see above) and the piezoelectric element 4.

[0147] Alternatively, the transponder 1 may comprise an inductor (not explicitly shown) for electrical impedance matching. The inductor is used in parallel with the capacitance of the piezoelectric element 4. Together with the inductor a resonant circuit is formed, which increases the voltage. Preferably, the inductor is sized so that the imaginary part of the impedance cancels out at the operating frequency, as occurs in a resonant circuit.

[0148] The electrodes 5 are electrically and mechanically connected to the transponder chip 2 via connection means 6, for example epoxy resin, which are formed elastically in order to compensate for vibrations of the piezoelectric element 4 and to provide an optimal connection of the piezoelectric element 4 to the transponder chip 2, as will be explained further below in connection with the description of the manufacturing method.

[0149] The transponder 1 is miniaturized. This means that the height h and / or volume of the transponder 1 is embodied in a very compact manner, in particular more compact than in the case of conventional transponders. The transponder 1 has a maximum height h<3 mm. The transponder 1 has a maximum height h<0.4 mm. 2 ~4mm 2 The transponder 1 can therefore be partially or completely embedded in the object 8, as is evident from FIG.

[0150] In the illustrated embodiment, the object 8 has a recess or blind hole 9 therefor, in which the transponder 1 is completely housed. The recess 9 is closed by a covering layer 10, so that no discernible defects can be perceived on the surface 8a of the object. In particular, the surface 8a of the object 8 can be treated during its lifetime without affecting the function of the transponder 1.

[0151] In an alternative embodiment (not explicitly shown), the transponder 1 can also be glued to a free surface or a recess of the object 8. This presupposes a cavity or a free surface of the object 8. In this case, the transponder 1 is not completely integrated inside the object 8.

[0152] In an alternative embodiment (not explicitly shown), the transponder 1 can be introduced into the object 8 within the framework of additive manufacturing (3D printing). In this case, the transponder 1 can be embedded in a starting material. Subsequently, further material can be produced via the starting material, so that the transponder 1 is completely embedded in the finished object 8.

[0153] Due to the miniaturization of the transponder 1, it can be optimally used for determining the location at the same time as identifying or authenticating the object 8. The miniaturized acoustic transponder 1 can also be used as an input element. For this purpose, a display (not explicitly shown) can be attached, for example glued, to the surface of the object 8. In that case, authentication first allows access to input information, and location allows operating the display on the object 8.

[0154] As already mentioned above, the transponder 1 is integrated into an acoustic transmission system (not explicitly shown).

[0155] The acoustic transmission system has a primary side and a secondary side. On the primary side, the transmission system comprises a transmitting unit, a receiving unit (reader) and an electro-acoustic transducer.

[0156] The transponder 1 is located on the secondary side of the transmission system and is, for example, completely integrated into the object 8. The transponder 1 receives a receive signal output by a transmitting unit and transmits a transmit signal 8. In that case, acoustic waves are used for the transmission of information, for example for the purpose of identifying the object 8.

[0157] If the transponder 1 is integrated, for example, in the shank of a drill, the shank is stored in the manufacturing machine so that it can be automatically re-clamped in the chuck when the workpiece is not in use.

[0158] This companion piece, in which the drill remains, can be equipped with a corresponding acoustic reader and possibly also contain an acoustic coupling medium (gel, oil, etc.). In that case, the reader has a larger piezoelectric element to ensure a good connection at all times. In this way, the stored ID numbers of the tools can be read out, for example, and their service life can be updated in the system.

[0159] It is also possible to house the acoustic reader in the chuck of the machine tool that receives the tool or the shank of the tool, so that measurement data can be recorded from the tool and incorporated into the machining process.

[0160] It is also possible to identify a 3D printed part when it is held by a gripper for assembly with other parts. The gripper, in this case, contains an acoustic reader, and the gripping process allows for the mechanical coupling to the workpiece necessary to create an acoustic channel for the sound waves.

[0161] In the following we describe a method for manufacturing a miniaturized transponder 1, preferably the transponder 1 described above, which method comprises the following steps:

[0162] In a first step A), a number of transponder chips 1 are provided. The transponder chips 1 are NFC chips, preferably operating in the frequency range of 9-14 MHz. The transponder chips 1 comprise a number of integrated circuits on a wafer.

[0163] The transponder chips 1 each comprise two connection elements 3. The connection elements 3 preferably comprise gold. The transponder chips 1 each have a maximum height of 170 μm.

[0164] In the next step B), a number of piezoelectric elements 4 are provided as signal transducers. The piezoelectric elements 4 are formed in the shape of a disk and comprise, for example, PZT. The piezoelectric elements 4 have a maximum height of 300 μm, preferably 200 μm.

[0165] Conductive material 7 (electrodes 5) is formed on the bottom surface 4b and top surface 4a of the piezoelectric element 4, and preferably on at least one side surface, for electrical contact of each piezoelectric element 4. The electrodes 5 comprise an elastic material, preferably silver. The elasticity of the conductive material 7 ensures that the electrodes 5 do not break under pressure when the piezoelectric element 4 is connected to the transponder chip 2.

[0166] In a further step C), connection means are provided, such as for example an adhesive. The connection means preferably comprises an epoxy resin and is elastic. The elasticity of the connection means 6 is important for compensating the vibrations (thickness vibrations) of the piezoelectric element 4.

[0167] In a next step D), the electrical and mechanical connection of the transponder chip 2 and the piezoelectric element 4 is made with the aid of connection means 6. In particular, each piezoelectric element 4 and each transponder chip 2 are connected to each other by means of a direct chip attach / flip chip assembly.

[0168] For this purpose, the wafer is rotated together with the transponder chip 2, so that the connection elements 3 are electrically contacted on the corresponding surfaces of the electrodes 5 of each piezoelectric element 4. The connection means 6 are then intended to enable a permanent mechanical connection. The connection means 6 shrink somewhat during hardening, thus pressing the connection elements 3 of the transponder chip 2 against the corresponding contact surfaces of the electrodes 5. At the same time, the connection means 6 are intended to remain somewhat elastic in order to apply the correct amount of force to the transponder chip 2 and the piezoelectric elements 4. For this reason, the electrodes 5 must also be somewhat elastic.

[0169] In a further step, a coating or surface passivation can be applied, which helps to protect against corrosion and may also serve to isolate the upper surface of the transponder 1 from pressures and temperatures such as those temporarily encountered during additive manufacturing.

[0170] In a final step E), separation into individual components takes place in order to produce a large number of miniaturized transponders 1.

[0171] Figure 4 shows a further embodiment of a miniaturized acoustic transponder 1. The acoustic transponder 1 of Figure 4 (similar to the transponders 1 of Figures 5 to 7) is designed to provide a communication channel for the transmission of information and energy by material waves, in particular through metallic surfaces.

[0172] The acoustic transponder 1 is characterized in that information processing, for example in the sense of receiving commands and responses with an identification number, is carried out entirely within a silicon chip (transponder chip 2) and not by a reflector for acoustic surface waves (SAW transponder).

[0173] The transponder 1 comprises the following components, as already explained in relation to FIGS. 1 to 3: a transponder chip 2 (preferably made of silicon as a bare die), a piezoelectric element 4 having an upper surface 4a and a lower surface 4b, operating as a thickness oscillator (preferred ratio of diameter to thickness <1:20); - electrodes 5 (in particular the upper electrode 5a and the lower electrode 5b). The characteristics and functions described above for these components also apply to the embodiments of acoustic transponder 1 described below.

[0174] The transponder chip 2 is mechanically fixed at its featureless back side to the piezoelectric element 4 by means of connecting means 6, for example adhesive. An electrical connection (connecting element 20) between the transponder chip 2 and the piezoelectric element 4 can be effected by bonding. In the simplest case, for a pure ID transponder (which responds to a reader inquiry with a unique identification number), two connections are required, leading from the connecting surfaces of the two electrodes 5, 5a, 5b of the piezoelectric element 4.

[0175] The transponder 1 is particularly suitable for bonding to the surface of a metallic object 8, such as a metal pipe. Preferably, the material of the object 8 (e.g., a metal plate) is homogeneous, with some surfaces intended for bonding to the piezoelectric element 4 and other surfaces intended not for bonding. This can be achieved by a thin adhesive layer (between the metal plate and the piezoelectric element 4), as will be explained further below. The acoustic waves of the transponder 1 are directed into the material (e.g., the metal plate) substantially perpendicular to the surface.

[0176] In one embodiment, the metallized top surface (top electrode 5a) of the piezoelectric element 4 is patterned (see, for example, structure 26 in FIGS. 6 and 7). The top electrode 5a may be patterned in the form of a layout to provide a connection surface for the inductor 21, which will be described in more detail below. By patterning the top electrode 5a, the inductor 21 may be assembled using a reflow soldering method, or alternatively, by conductive adhesive.

[0177] The patterning of the top electrode 5a can be done already before the process of poling of the piezoelectric element 4, with the aim of keeping part of the surface of the piezoelectric element 4 free from electrically excited thickness vibrations during subsequent operation. In other words, the piezoelectric element 4 can be divided by the purposeful patterning of the top electrode into areas with stronger resonant thickness vibrations and areas that are not polarized and therefore remain quiet / non-vibrating.

[0178] The transponder 1 further comprises a protective element 22. In this embodiment, the protective element 22 comprises a casting compound 27. The casting compound 27 is formed on the top surface 1a of the transponder (thus corresponding to the back surface of the transponder 1 facing away from the object 8). The casting compound 27 completely encapsulates the top surface 1a and at least a part of the side surface 1b of the transponder 1. The casting compound 27 protects the transponder 1 from external influences.

[0179] The casting compound 27 may be transparent to allow the acoustic transponder to emit light into the interior space of, for example, a metal pipe. The casting compound 27 may be opaque to prevent light from affecting the function of the transponder 1. The casting compound 27 may contain magnetizable particles.

[0180] To prevent the casting compound 27 from covering most of the surface of the inner piezoelectric element 4, a non-wettable structure / sphere can be used as an underlayer.

[0181] Furthermore, it is possible to provide a thin circuit board (not explicitly shown) between the piezoelectric element 4 and the casting compound 27. This circuit board can have a relief structure on its underside, so that only a small percentage of the area of ​​the circuit board is in contact with the piezoelectric element 4.

[0182] The transponder 1 further comprises the above-mentioned inductor 21. The inductor 21 is electrically connected in parallel to the two electrodes 5, 5a, 5b. In this embodiment, the inductor 21 is designed as a separate electrical component. For example, the inductor 21 is formed in an SMD format. A wire-wound or ceramic multilayer structure is possible here.

[0183] The transponder 1 may have the shape of, for example, a flat cylinder. In use, the transponder 1 is acoustically connected to a flat, smooth metal surface, for example by using a coupling element with a specific layer thickness. The coupling element may comprise an adhesive, for example, an epoxy resin.

[0184] In a further embodiment (see in this regard Fig. 5), the transponder 1 may further comprise an interface 23 for external connection of the transponder 1. In this embodiment, the interface 23 is electrically and mechanically connected to the upper electrode 5a and protrudes from the top surface of the transponder 1 for electrical connection with external electronic components.

[0185] The transponder 1 may further comprise a further protective element 22, for example a protective layer or membrane 24 (FIG. 5). The membrane 24 is formed on the lower surface 1b of the transponder 1. Preferably, the membrane 24 is glued to the lower surface 4b of the piezoelectric element or to the lower electrode 5b. The membrane 24 may comprise steel, for example a steel plate. The membrane 24 may also be magnetic.

[0186] To couple the transponder 1 to the metal surface of the object 8, the membrane 24 can be glued to the metal surface. A magnetic connection to the metal surface of the object 8 to form a detachable connection is also conceivable. The surface of the membrane 24 is larger than the surface of the piezoelectric element 4 or the transponder 1 to ensure an optimal connection to the metal surface.

[0187] In order to achieve good acoustic contact between the membrane 24 or the piezoelectric element 4 and the acoustic channel (surface of the metallic object 8), the coating on the surface of the membrane 24 or the piezoelectric element 4 may be provided with a thin elastic layer (not explicitly shown). This has the purpose of largely filling the cavity formed due to the surface roughness of the opposite metal surface with a medium having a significantly higher acoustic impedance than air. The efficiency of the acoustic coupling may thereby be significantly increased.

[0188] To produce a housing for the acoustic transponder 1, a protective element 22 in the form of a rim along the periphery of the transponder 1 can also be provided (not explicitly shown in FIG. 5; see, for example, rim 28 in FIG. 6). In other words, a rim is formed along the side surface 1c of the transponder 1. In that case, the height of rim 28 is greater than the height of the components in the interior region of the transponder 1. The volume inside rim 28 can then be filled with a casting compound 27 so that the internal components are protected. Rim 28 can, for example, be placed on the above-mentioned membrane 24 to obtain a transponder 1 protected on all sides (top surface 1a, side surface 1c, bottom surface 1b).

[0189] To achieve a holding force of the acoustic transponder 1 on a metal surface, the edge 28 can contain a magnetic material. The edge 28 can be designed in the form of a ring magnet. As mentioned above, the membrane 24 can also be correspondingly magnetic or magnetized.

[0190] To protect the transponder 1 from the release of contaminated gases, steel is suitable as a material for the edge 28 / membrane 24. In many applications for sensors in gas and pressure vessels made of stainless steel, it is required to use only the inner stainless steel surface and to exclude gas contamination. Therefore, it is also possible to embody the membrane 24 and edge 28 as a sleeve with a closed surface.

[0191] If the counterpart of the acoustic transmission system outside the tube is also suitably magnetic, a holding force is obtained while simultaneously aligning the two acoustic counterparts (primary and secondary).

[0192] If the transponder 1 is coupled to a curved surface, i.e. for example mounted inside a pipe, the length of the vibrating piezoelectric element 4 relative to the inner diameter of the pipe is important in order to keep losses due to destructive interference low. In this case, the support surface of the acoustic transponder 1 can therefore be substantially rectangular with its short side along the pipe diameter and its long side along the pipe length (straight piece).

[0193] In a further possible embodiment, the inductor 21 is laid out and designed as a planar coil (designed as a transparent passive repeater without the transponder chip 2, not explicitly shown). In order to obtain a large area electrode shape for the piezoelectric element 4 independent of the planar coil, a stacking sequence of piezoelectric element 4 - upper electrode 5, 5a - insulating and / or magnetic insulating layer (e.g. ferrite layer) - planar coil can be used.

[0194] The planar coil also acts as an emitter of the H alternating magnetic field, which is the same as in conventional NFC technology. Used as a loop antenna, this structure (even without the transponder chip 2) creates a transparent transducer between an H-alternating magnetic field and sound waves. Glued to a flat, smooth metal surface, this transducer converts NFC communication via the H-alternating magnetic field in the air into material waves. A similar transducer glued to an opposite metal surface would correspondingly convert the material waves into an H-alternating magnetic field. This allows a transparent passage / transparent passive repeater for NFC signals to be achieved by the metal.

[0195] The transparent transponder design is suitable (due to the characteristics of the channel) for NFC transmission standards in the 13.56 MHz frequency range and can support protocols according to ISO / IEC 14443 and ISO / IEC 15693. Since an electrical load changes the elastic properties of the piezoelectric element 4 and therefore a regular modulation (combination of phase and amplitude modulation) can be recognized in the signal reflected on the transponder side for the transponder, the method of load modulation by the subcarrier frequency used in these two standards can also be used.

[0196] The embodiment may further be configured so that the region of the acoustic wave below the piezoelectric element 4 has a small area into the material perpendicular to the surface.

[0197] Similarly, the transparent repeater can comprise two or more inductors 21 (not explicitly shown). For example, the repeater can comprise two inductors designed as planar coils. A first planar coil is formed above the piezoelectric element 4 (i.e., above the upper surface 4a of the piezoelectric element). The first planar coil has a small area (e.g., a diameter of 5 mm). A second planar coil is formed below the piezoelectric element 4. The area of ​​the second planar coil is larger than the area of ​​the first planar coil. The second planar coil is inductively coupled to the first planar coil. The second planar coil is arranged, for example, on a ferrite foil for magnetic insulation.

[0198] The first planar coil can be extended to a larger antenna in the usual format of an ID card (ID1 according to ISO / IEC 7810 or antenna classes 1 to 6 according to ISO / IEC 14443) by coupling it to a second or secondary planar coil.

[0199] A second planar coil (secondary antenna) of larger area can be designed as a thin "patch" on the surface of the object 8, especially a metal one. The second planar coil can be a separate resonant circuit close to 13.56 MHz, with the secondary coil connected to an appropriate capacitance. The second element ("patch" or secondary coil) is therefore connected to the first planar coil by inductive coupling (the two coils are spatially close to each other). In practice, the "patch" can have a hole the size of the first planar coil, which facilitates in-plane coupling during assembly.

[0200] 6 shows a further embodiment of an acoustic transponder 1. The transponder 1 comprises a transponder chip 2, a piezoelectric element 4, electrodes 5, 5a, 5b, an inductor 21 and a connecting element 20. For the properties and functions of these components, reference is made to the above description.

[0201] The transponder 1 of Fig. 6 additionally comprises an intermediate element 25. The intermediate element 25 is arranged between the transponder chip 2 and the piezoelectric element 4. The intermediate element 25 may comprise a printed circuit board (PCB). The transponder chip 2 is arranged on and fixed to the upper surface of the intermediate element 25 via connecting means 6, for example an adhesive.

[0202] With the aid of the intermediate element 25, the contact surface of the transponder chip 2 and / or the casting compound 27 on the upper surface 4a of the piezoelectric element 4 can be reduced. In other words, the intermediate element 25 causes a smaller proportion of the transponder chip 2 and / or the casting compound 27 to be placed on the upper surface 4a of the piezoelectric element 4 or on the upper electrode 5a. The quality of the natural resonance in the thickness vibration mode of the piezoelectric element 4 decreases as the support becomes more all-round. However, this is detrimental to the efficiency of the conversion between mechanical and electrical amplitudes.

[0203] The intermediate element 25 can be patterned. In particular, the lower surface of the intermediate element 25, i.e., the surface facing the piezoelectric element 4, can have a structure 25a. For example, the intermediate element 25 can have short cylindrical posts protruding from a plane (the lower surface of the intermediate element 25). Alternatively, honeycomb walls, i.e., polygonal structures, are possible. In this way, only a small percentage of the surface of the piezoelectric element 4 can be mechanically contacted (e.g., 10%), while the rest of the surface of the piezoelectric element 4 can vibrate freely. The piezoelectric element 4 is thereby less affected by thickness vibrations. Furthermore, by appropriately selecting the percentage of surface contact, the influence can be targeted and utilized.

[0204] In addition to the mechanical connection, there must also be an electrical connection between the two electrodes 5a, 5b of the polarized piezoelectric element 4 and the intermediate element 25. The same applies to the electrical connection to the connecting element 20 and therefore to the transponder chip 2 on the upper surface of the intermediate element 25.

[0205] One possibility for this is to provide a metallized surface with a specific structure for the intermediate element 25. For example, it is possible to sputter a structure and subdivide it by means of a mask in order to create corresponding parallel contact surfaces. The metallized intermediate element 25 can then be mechanically and electrically connected to the similarly metallized piezoelectric element 4, for example by reflow soldering.

[0206] Alternatively, so-called 3D electronic moulded parts can be used, i.e. non-conductive plastic moulded parts which can be provided with conductor tracks and even internal connections by means of laser treatment and further processes.

[0207] The intermediate element 25 can be designed to be elastic. In particular, the intermediate element 25 can have vibration-damping properties and therefore, in addition to a precise layout as a support surface for the components and / or transponder chip 2, can also provide vibration isolation or vibration reduction. Preferably, the intermediate element 25 is designed so that vibrations due to acoustic waves, in particular in the 13.56 MHz range, are well absorbed. This can be achieved in cooperation between the relief shape and the material properties.

[0208] The intermediate element 25 may alternatively or additionally have thermal insulating properties, which may therefore contribute to protecting the temperature-sensitive transponder chip 2 from short-term high temperature phases in certain applications due to its large thermal time constant.

[0209] There may be further layouts for implementing circuits on the intermediate element 25. The transponder chip 2 and the matching network (inductor 21) may be assembled thereon.

[0210] In particular, further chips with sensor or analog-to-digital converter functionality can be connected to the electrical interfaces of the transponder chip 2 on the layout on the intermediate element 25. Electrical contact embodiments (e.g. pogo pins, flat contact areas that can also be assembled in the form of rings, etc.) can also be assembled, which can later protrude from the packaging / casting compound 27 and be electrically contacted. For example, it is possible to connect an analog pressure sensor in the form of a resistive bridge to the functional subassembly described here.

[0211] Furthermore, in order to reduce the overall height of the transponder 1, it is also possible to mount the inductor 21 directly on the piezoelectric element 4 and mount the intermediate element 25 on the remaining surface of the piezoelectric element 4 (not explicitly shown).

[0212] As already explained in connection with Figures 4 and 5, the transponder 1 can further comprise a protective element 22 in the form of a casting compound 27. The casting compound 27 completely encapsulates the upper surface 1a of the transponder 1. In this embodiment, the protective element 22 further comprises a rim 28 as described above. The rim 28, which is at least partially filled with the casting compound 27, can be formed integrally with the intermediate element 25 or can be provided as a separate part. If the rim 28 is formed integrally with the intermediate element 25, the intermediate element comprises in its outer region a circumferential raised portion (collar) which serves as the rim 28 (see Figure 6).

[0213] The protective element 22 further comprises a membrane 24 as described above, which protects the underside of the transponder 1 from external influences. In this embodiment, the membrane 24 also extends partially over the side surface 1b of the transponder 1 or of the intermediate element 25. An edge 28 may rest on the membrane 24 (not explicitly shown).

[0214] Furthermore, the transponder 1 may also comprise an interface 23 for external connection of the transponder 1. In this embodiment, the interface 23 is formed at the edge 28 to allow connection to external components.

[0215] 7 shows a further embodiment of a miniaturized acoustic transponder 1. The transponder 1 comprises a transponder chip 2, a piezoelectric element 4, electrodes 5, 5a, 5b, an inductor 21, a protective element 22 (membrane 24, casting compound 27, edge 28) and an intermediate element 25.

[0216] In contrast to the transponder chip 2 according to the above embodiment, the transponder chip 2 in Fig. 7 is designed as a packaged IC, not as a bare die, and for all other characteristics and functions of the listed common components, reference is made to the above embodiment.

[0217] In this embodiment, a circuit board 29 (PCB) with conductor tracks is arranged between the transponder chip 2 and the intermediate element 25. The circuit board 29 establishes an electrical connection between the electrodes 5, a, 5b and the transponder chip 2 or the inductor 21. In this embodiment, the above-mentioned connection means 20 (wire bonds) can be omitted.

[0218] The description of the subject matter presented herein is not limited to individual specific embodiments, but rather the features of the individual embodiments can be combined with each other in any way that makes sense technically. [Explanation of symbols]

[0219] 1 transponder 1a Top of transponder 1b Underside of transponder 1c Side of the transponder 2 transponder chips 3 Connection Elements 4 Piezoelectric element 4b Top surface 4b Bottom side 5 electrodes 5a Upper electrode 5b Bottom electrode 6. Connection Methods 7 Conductive materials / electrode materials 8 objects 8a Surface of an object 9 Recess 10 Covering layer h Transponder height 20 Connecting Elements 21 Inductor 22 Protection Elements 23 Interface 24 membrane 25 Intermediate element 25a Structure of intermediate element 26 Electrode structure 27 Casting Compound 28 Edge 29 Circuit Board

Claims

[Claim 1] An acoustic transponder (1) for an acoustic transmission system, comprising: a transponder chip (2); a piezoelectric element (4) for converting a carrier frequency into a voltage; The transponder (1) has a miniaturized structure.

Images