Ultrasonic sensor and method for producing an ultrasonic sensor

Abstract

The invention relates to an ultrasonic sensor (1) with a micro-electromechanical sensor unit (2) for generating and capturing an ultrasonic signal, a sensor housing (3) for receiving the sensor unit (2), a housing board (5) and a sensor-head board (6), which is arranged in the sensor housing (3), is at a distance from the housing board (5) and has a signal-processing unit (7) for processing signals from the micro-electromechanical sensor unit (2), wherein the sensor-head board (6) has a base portion (8), for receiving the signal-processing unit (7), and a connecting portion (9), which is formed integrally with the base portion (8) and is intended for the electrical connection of the sensor-head board (6) to the housing board (5), and wherein the connecting portion (9) has a lower flexural rigidity than the base portion (8). The invention also relates to a method (100) for producing an ultrasonic sensor (1) with a micro-electromechanical sensor unit (2).

Description

[0001] Description

[0002] title

[0003] Ultrasonic sensor and method for producing an ultrasonic sensor

[0004] The invention relates to an ultrasonic sensor with a microelectromechanical sensor unit and a method for producing such an ultrasonic sensor.

[0005] State of the art

[0006] Ultrasonic sensors with microelectromechanical sensor units and methods for their manufacture are known from the prior art. Microelectromechanical sensor units are also referred to as micromechanical sensor units or MEMS sensor units.

[0007] DE 10 2020211 538 A1 discloses a micromechanical component for a sound transducer device, a sound transducer device, and a method for producing a micromechanical component for a sound transducer device. The sound transducer device can be designed as an ultrasonic transducer. The micromechanical component has a piezoelectric element with an electrical contact connection and can be connected to a control circuit using flip-chip technology such that the piezoelectric element can be electrically connected to the control circuit via the electrical contact connection.

[0008] DE 102018 105 502 A1 describes an ultrasonic sensor assembly comprising a first sensor housing part, a transducer element arranged at least partially within the first sensor housing part for generating ultrasonic vibrations, at least one flexible electrical connection means electrically connected to the transducer element and contactable or electrically contactable with at least one electronic component, and a guide device in which the flexible electrical connection means is at least partially guided. Furthermore, a method for assembling such an assembly is described.

[0009] Disclosure of the invention

[0010] According to the features of independent claim 1, an ultrasonic sensor is proposed with a microelectromechanical sensor unit for generating and detecting an ultrasonic signal, a housing board, a sensor housing for receiving the sensor unit and a sensor head board arranged in the sensor housing and spaced from the housing board, with a signal processing unit for processing signals from the microelectromechanical sensor unit, wherein the sensor head board has a base section for receiving the signal processing unit and a connecting section formed integrally with the base section for electrically connecting the sensor head board to the housing board, and wherein the connecting section has a lower flexural rigidity than the base section.

[0011] In other words, it is proposed to establish an electrical connection between two circuit carriers of the ultrasonic sensor which are spaced apart from one another by arranging on one of the two circuit carriers a one-piece connecting part which is more flexible than the circuit carrier, by means of which the spatial distance between the circuit carriers can be bridged in a flexible manner and by means of which the two circuit carriers can be electrically connected to one another.

[0012] An ultrasonic sensor according to the proposed features has the advantages of a smaller number of components and reduced component complexity due to the connecting section formed integrally with the sensor head board. The proposed ultrasonic sensor is also characterized by easier manufacturability, since a separate manufacturing step for contacting the sensor head board with a separate connecting means is eliminated, particularly considering the limited space in the sensor housing, which complicates assembly and contacting. Handling the sensor head board and the connecting section, as well as their placement in the narrow sensor housing, is significantly simplified by their integral design and the partially reduced flexural rigidity in the connecting section.Furthermore, the one-piece design of the connecting section with the sensor head board improves the quality of the electrical connection compared to a subsequently attached connector. Shielding measures can be implemented directly on the sensor head board during production to increase the electromagnetic compatibility of the assembly. Due to the partially reduced flexural rigidity, the connecting section can be optimally aligned within the sensor housing and adapted to the existing distance between the sensor head board and the housing board.

[0013] An ultrasonic sensor can be a sensor device configured for signal-time-based distance measurement to objects by transmitting and receiving a reflected ultrasonic signal. Ultrasonic sensors can be arranged, for example, as distance sensors on vehicles, particularly on bumpers or other body components, to support driver assistance functions or autonomous driving functions of the vehicle.

[0014] A microelectromechanical sensor unit, also known as a MEMS sensor unit, can comprise, for example, one or more semiconductor-produced sensor components with mechanical and electrical microstructures, for example, microstructures with dimensions in the micrometer and / or nanometer range. A microelectromechanical sensor component can be suitable for implementation as a system-on-chip (SoC), so that the sensor component can be designed as a MEMS chip. Microelectromechanical sensor units can, for example, be used as miniaturized sensors in confined spaces. The microelectromechanical sensor unit used for the ultrasonic sensor can, for example, comprise a sensor component designed as a microelectromechanical transceiver, which can be configured to generate and receive an ultrasonic signal at a time-shifted time using a movable structure such as a micromembrane.According to one embodiment, the microelectromechanical sensor component can interact with a connected membrane component to generate an ultrasonic signal and / or receive a reflected ultrasonic signal. In this case, the sensor component and the membrane component together form the microelectromechanical sensor unit. Furthermore, it is conceivable for the microelectromechanical sensor unit to have a plurality of microelectromechanical sensor components, i.e., at least two microelectromechanical sensor components. Depending on the embodiment, these can each be designed, for example, as an ultrasonic transceiver, i.e., as a combined transceiver, or one of the sensor components can be designed as an ultrasonic transmitter and another of the sensor components can be designed as an ultrasonic receiver. An ultrasonic signal is a sound signal with a frequency above the human audible frequency range.Ultrasonic signals, for example, can have a frequency between 20 kHz and 1 GHz.

[0015] The sensor housing can be configured to mechanically accommodate components of the ultrasonic sensor, such as the microelectromechanical sensor unit, the sensor head board, and the housing board. The sensor head board and the housing board can be arranged, in particular, in an interior of the sensor housing to protect them from environmental influences. The sensor housing can also form an insulating cover for the sensor components and can be designed, for example, as a plastic housing. The sensor housing can have a housing base, which, according to one embodiment, has at least one recess or through-opening into which the microelectromechanical sensor unit is embedded.This allows the sensor unit to be protected within the sensor housing, yet simultaneously interact with the ultrasonic sensor's environment and transmit and receive ultrasonic signals with a long range largely unaffected by the sensor housing. If the sensor unit comprises a microelectromechanical sensor component and a membrane component interacting with it, the membrane component can form a component of the sensor housing that is integrally formed with the housing base or mechanically connected to the housing base. The membrane component can be connected to the sensor component by a material bond, for example, by adhesive bonding. The housing base of the sensor housing can, for example, have a circular basic shape to enable the most space-saving and compact design of the ultrasonic sensor.In addition, for example, a corresponding opening with a round geometry on a vehicle bumper can be easier to manufacture and more robust than an opening with a different, for example square, geometry.

[0016] The housing board can be a substantially rigid electrical circuit carrier, for example a printed circuit board (PCB). According to one embodiment, the housing board can have a driver unit, which can have, for example, a wiring element such as a transformer element or an inductor, as well as a driver circuit for controlling the transformer element or the inductor. The driver unit can form a transmitting unit of the ultrasonic sensor, which serves to provide the required transmitting energy for the ultrasonic signal to be transmitted by the microelectromechanical sensor unit. The housing board can, for example, be arranged in or on the sensor housing. The housing board is, in particular, spatially spaced from the sensor head board, so that they cannot be or are not electrically connected to one another by direct mutual contact.In particular, the housing board has a greater distance to the microelectromechanical sensor unit than the sensor head board.

[0017] The signal processing unit can be understood as a control circuit, which can be designed in particular as an integrated circuit, for example as an ASIC (application-specific integrated circuit). The signal processing unit is configured to process signals from the microelectromechanical sensor unit and can receive and evaluate sensor signals from the sensor unit, as well as perform control tasks. The signal processing unit can be accommodated by the base section of the sensor head board and can be mechanically or materially connected to the base section of the sensor head board, as well as electrically connected to it, for example by bonding or soldering contacts. In addition to the housing board, the sensor head board can form a second electrical circuit carrier for the ultrasonic sensor.Due to the integrally formed connecting section and the connection function implemented thereby between the circuit carriers, the sensor head board offers enhanced functionality compared to comparable prior art sensor head boards. The sensor head board also serves to accommodate the signal processing unit and, if applicable, other electrical components of the ultrasonic sensor and also enables an electrical and signal-related connection between the signal processing unit and the microelectromechanical sensor unit of the ultrasonic sensor. The sensor head board can, in particular, be arranged adjacent to the sensor unit or in its immediate vicinity in the sensor housing and can be electrically connected to the sensor unit, for example, by means of bond wiring or solder contacts.

[0018] According to the proposed features, the sensor head board has a base section and a connecting section formed integrally with the base section. The base section can be a partial region of the sensor head board, which can in particular be arranged on the housing base of the sensor housing. The base section can serve to accommodate the signal processing unit and, if appropriate, further electrical components of the ultrasonic sensor and establish an electrical connection between the signal processing unit and the microelectromechanical sensor unit. The base section can in particular extend substantially parallel to the housing base or rest on the housing base in a planar contact. When the sensor head board is in a planar state, its greatest extent can define a longitudinal extent of the sensor head board.The base portion may have a greater width extension perpendicular to the longitudinal extension than the connecting portion, wherein the width extension of the sensor head board is greater than the depth extension of the sensor head board.

[0019] The connecting section can, for example, be strip- or bar-shaped, with a substantially rectangular base area, for example, across the connecting section between the sensor head board and the housing board. The connecting section can have a greater length and width than depth. The connecting section can protrude from a side edge of the base section and, when the sensor head board is mounted in the sensor housing, can be angled or bent or diverted from the base section at a radius, for example, substantially perpendicularly, forming a C-shape or forming an S-shape of the connecting section.The connecting section can serve as the electrical connection between the sensor head board and the housing board, and thus, for example, also as an electrical connection between a driver unit and the microelectromechanical sensor unit. For this purpose, the connecting section can have corresponding electrical connection structures, such as conductor tracks and circuit elements. Accordingly, the connecting section can enable a structured electrical connection between the sensor head board and the housing board and can therefore be distinguished from a simple electrical conductor.

[0020] According to the proposed features, the connecting section has a lower flexural rigidity than the base section. Accordingly, the connecting section can be more easily elastically and / or plastically deformed under the action of force than the base section. A lower flexural rigidity of the connecting section can be achieved, for example, by its geometric design, such as a strip-shaped, narrower design compared to the base section, by a different internal structural design, or by a different material composition compared to the base section.The lower flexural rigidity of the connecting section ensures that the connecting section can be easily aligned in the sensor housing and positioned for connection to the housing circuit board independently of the base section, without compromising the stability of the base section and thus, for example, the quality of the connection between the base section and the electrical components arranged thereon or between the base section and the microelectromechanical sensor unit electrically connected to it. Accordingly, each of the two sections of the sensor head circuit board is optimally adapted to its intended function through different flexural rigidities and the resulting different flexibility. The design and manufacture of the sensor head circuit board can fundamentally be based on technologies and construction methods of flexible printed circuit boards, as will be explained in more detail below.Against this background, the sensor head board can also be summarized as a semi-rigid or semi-flexible sensor head board.

[0021] The flexibility of the connecting section achieved by the lower flexural rigidity of the connecting section compared to the base section can be provided in different degrees of flexibility depending on the design.

[0022] According to one embodiment, the connecting section can be designed as a predominantly flexurally flexible connecting section. A predominantly flexurally flexible connecting section can be understood as a non-dimensionally stable connecting section and can be described, for example, by a low modulus of elasticity. A flexurally flexible connecting section can experience large deformations even as a result of small force and moment loads. The flexurally flexible connecting section can be described, for example, simply as a flexible printed circuit board strip. A flexurally flexible connecting section can be associated with very high flexibility, thus enabling easy handling and allowing the connecting section to be easily connected to the housing board without significant mechanical stress.

[0023] According to an alternative embodiment, the connecting section can be designed as a predominantly dimensionally stable connecting section. A predominantly dimensionally stable connecting section can have a higher flexural rigidity or a higher modulus of elasticity than a flexible connecting section. A dimensionally stable connecting section can, for example, undergo deformation with a predominantly plastic deformation component through bending and remain in the assumed shape without any significant recovery. A dimensionally stable connecting section can, for example, be achieved by arranging a flexible element such as a copper element in the connecting section, which additionally provides advantageous electromagnetic shielding of the connecting section. A dimensionally stable connecting section can also, due to its dimensional stability, be more robust than a flexible connecting section.

[0024] According to one embodiment, the sensor head board can have a layer arrangement of electrically conductive and electrically non-conductive layers. This allows the mechanical and electrical properties of the sensor head board to be specifically influenced by means of an individual layer arrangement and defined with a high degree of design freedom. For example, the number and layer thickness of the individual electrically conductive and / or electrically non-conductive layers can vary according to the desired mechanical and electrical properties of the sensor head board. For example, the sensor head board can be mechanically stiffened by an increased number or layer thickness of an electrically non-conductive layer. An electrically conductive layer can, for example, comprise a metal, in particular copper. The electrically conductive layer can be structured, for example by forming electrical conductor tracks in a carrier material.An electrically non-conductive layer can, for example, comprise a plastic material, in particular a polyimide. The electrically non-conductive layer can form a carrier material, electrical insulation, and oxidation protection for the electrically conductive layer or conductor track. The layers of the layer arrangement can, for example, be laminated to one another. The layer arrangement can comprise multiple electrically conductive and / or multiple electrically non-conductive layers. According to one embodiment, the sensor head board can be designed as a flexible printed circuit. Flexible printed circuits are, for example, circuits based on polyimide film to which electrically conductive structures and / or components are applied.

[0025] According to one embodiment, the base section can have a layer arrangement that differs from the connecting section. This allows the mechanical and electrical properties of the sensor head board to be designed differently locally by means of an individual layer arrangement. In particular, the connecting section can be provided with lower flexural rigidity by a layer arrangement that differs from the base section. For example, the sensor head board can be mechanically stiffened in the base section by a higher number or layer thickness of an electrically non-conductive layer than in the connecting section. Conversely, the sensor head board can be designed to be mechanically more flexible in the connecting section by a lower number or layer thickness of an electrically non-conductive layer than in the base section.In other words, it is possible to achieve a lower flexural rigidity of the connecting section by using an internal structural design that differs from the base section in the form of a different layer arrangement. In principle, it is not excluded to alternatively or additionally reduce the flexural rigidity in the area of ​​the connecting section by using a different material in at least one layer of the layer arrangement.

[0026] According to one embodiment, the base section can have a hexagonal outer contour. This allows for greater surface utilization compared to other basic geometric shapes, such as a rectangular outer contour. Particularly in embodiments of the ultrasonic sensor with a sensor housing having a housing base with a substantially circular basic shape, a base section with a hexagonal outer contour can achieve a polygonal approximation of the outer contour to the available floor area of ​​the housing base.At the same time, a sensor head board with a hexagonal base section can be easily manufactured. In particular, with a hexagonal outer contour of the base section, a large number of sensor head boards can be provided in the form of a board panel with the sensor head boards arranged in a space-saving manner, and the sensor head boards can be separated from the board panel with minimal waste. The additional usable space allows the signal processing unit and optionally other components of the ultrasonic sensor to be housed safely and reliably on the base section of the sensor head board while maintaining the technically required clearances.In particular, the additional usable space makes it possible to accommodate the entire receiver stage of the ultrasonic sensor on the base section of the sensor head board, eliminating the need to arrange individual components on the housing board due to space constraints. By arranging the signal processing unit on the sensor head board, the distance between the microelectromechanical sensor unit and the signal processing unit can be significantly reduced compared to arranging the signal processing unit on the housing board, thereby reducing parasitic capacitances and optimizing the electromagnetic compatibility of the ultrasonic sensor on its receiving path.

[0027] According to one embodiment, the base section can have a centering contour for aligning the sensor head board in the sensor housing. This can ensure optimal arrangement of the sensor head board even in confined space conditions in the sensor housing. Furthermore, the sensor head board can be fixed in its orientation in the sensor housing by means of the centering contour. The sensor housing, for example the housing base of the sensor housing on which the base section is arranged or a side wall of the sensor housing, can have a corresponding counter-contour for centering. For example, the centering contour can represent a geometric negative form of the counter-contour or vice versa, so that the centering contour and the counter-contour can engage with one another. The centering contour can, for example, be designed as an indentation and the counter-contour can correspondingly be designed as a projection, or vice versa.The centering contour can, for example, be partially circular, in particular semicircular. The base section can have multiple centering contours, for example, two centering contours arranged opposite one another. If the base section has a hexagonal outer contour, the centering contour can, for example, be arranged at a corner point of the outer contour, or two centering contours can be arranged at opposite corner points of the outer contour.

[0028] According to one embodiment, the connecting portion may comprise a

[0029] Widening in a connection region of the connecting section provided for connection to the housing board. In other words, the connecting section can have a wide connection region and a narrow coupling region between the connection region and the base section of the sensor head board. In other words, the connection region can have a greater width than a coupling region of the connecting section running between the connection region and the sensor head board. A widening or a width can refer in particular to an extension of the connecting section transverse to its longest extension, which describes a length or longitudinal extension of the connecting section. The width and the length can be significantly greater than the depth of the, for example, flat connection section. The connecting section can, for example, widen into a wing-shaped connection region.By widening the connection section in the connection area, a larger connection surface is provided for connecting the connection section to the housing board, which simplifies contacting accordingly. In particular, a widened connection area also allows for connection processes that would otherwise be technically impossible due to a smaller contact point distance, such as bar soldering processes. This can significantly reduce machine costs, the process time for establishing the electrical connection between the housing board and the sensor head board, and thus the manufacturing costs of the ultrasonic sensor.

[0030] According to one embodiment, the microelectromechanical sensor unit can be designed as a piezoelectric ultrasonic transducer. This allows for a robust and cost-effective sensor unit with high measurement accuracy and a precisely focusable ultrasonic signal to be provided. Microelectromechanical, piezoelectric ultrasonic transducers are also referred to as PMUTs (piezoelectric micromachined ultrasonic transducers) and enable good integration of the sensor unit into a compact ultrasonic sensor. The invention also relates to a method for producing an ultrasonic sensor with a microelectromechanical sensor unit, comprising the steps:

[0031] - Providing a sensor housing, a microelectromechanical sensor unit, a housing board and a sensor head board with a signal processing unit;

[0032] - Establishing a mechanical and electrical connection between the microelectromechanical sensor unit and the sensor head board;

[0033] - arranging the sensor unit, the sensor head board and the housing board in the sensor housing; and

[0034] - Establishing an electrical connection between the sensor head board and the housing board by means of a connecting section which is integrally formed with a base section of the sensor head board and which has a lower bending stiffness than the base section, by connecting a connecting region of the connecting section to the housing board.

[0035] The method according to the proposed features enables efficient production of the ultrasonic sensor. The ultrasonic sensor can be designed, in particular, according to one of the features described above. By establishing an electrical connection between the sensor head board and the housing board by means of a connecting section formed integrally with a base section of the sensor head board, which has a lower flexural rigidity than the base section, manufacturing steps can be eliminated compared to known methods for manufacturing comparable ultrasonic sensors. The process time can be shortened due to the reduced number and complexity of the process steps, thus increasing the cost-effectiveness of the process.

[0036] According to one embodiment, the sensor head circuit board can be provided by separating it from a circuit board panel comprising a plurality of sensor head circuit boards. With a circuit board panel comprising a plurality of sensor head circuit boards, an economical and cost-optimized provision of the sensor head circuit board can be achieved, wherein separating the sensor head circuit board from a circuit board panel is possible in a simple manner, for example by milling, laser cutting, or punching. In the circuit board panel, the sensor head circuit boards can be provided such that the base section and the connecting section are arranged flat in a common plane. This allows a circuit board panel comprising a plurality of sensor head circuit boards to be easily manufactured. The circuit board panel can be produced, for example, by laminated electrical and non-electrical layers analogous to the production of flexible printed circuit boards.

[0037] According to one embodiment, before arranging the sensor head board in the sensor housing, the connecting section of the sensor head board can be bent away from the base section, for example, essentially perpendicularly or forming a C-shape or S-shape of the connecting section. This allows for a simple pre-alignment of the connecting section and facilitates the arrangement of the sensor head board in the sensor housing. Bending the connecting section before arranging the sensor head board in the sensor housing is particularly advantageous if the connecting section is designed as a predominantly dimensionally stable connecting section, so that the bent orientation of the connecting section is maintained during the further process sequence.Depending on the shape of the sensor housing, further bends, kinks or angles can be created on the connecting section before or during the arrangement of the connecting section in the sensor housing.

[0038] Furthermore, it can be provided that a mechanical and electrical connection is established between the microelectromechanical sensor unit and the sensor head board before the sensor head board is arranged in the sensor housing. For example, it is conceivable that before the sensor head board is arranged in the sensor housing, the microelectromechanical sensor unit is firmly bonded to the sensor head board and an electrical contact is established between the sensor unit and the sensor head board, for example by means of bond wiring. According to one embodiment, the sensor head board can be firmly bonded to a housing base of the sensor housing during its arrangement in the sensor housing.For this purpose, for example, after establishing the electrical connection between the sensor head board and the sensor unit, an adhesive can be applied to the housing base and / or to the sensor head board, the sensor head board can be placed on the housing base and curing of the adhesive can be enabled, in particular supported by thermal treatment or UV radiation.

[0039] After the sensor head board has been positioned in the sensor housing, the connecting section can be aligned within the sensor housing so that subsequent connection of the housing board can be carried out quickly and easily. For example, the connecting section can be laid along a housing wall of the sensor housing, or bent or folded according to the housing contour. The provided housing board can then be positioned in or on the sensor housing and secured therein, for example by hot-staking. A connection area of ​​the connecting section can then be prepared, for example by bending it, for connection to the housing board, and the connection can be made.

[0040] According to one embodiment, the connection area of ​​the connecting section to the housing board can be connected using a hot-bar soldering process. This can significantly reduce the machine costs, the process time for establishing the electrical connection between the housing board and the sensor head board, and accordingly the manufacturing costs of the ultrasonic sensor.

[0041] In general, in the context of this application, the words "a / an," unless expressly defined otherwise, are not to be understood as a number, but as an indefinite article with the literal meaning of "at least one / an." The invention permits various embodiments and is explained in more detail below using exemplary embodiments with the accompanying drawings. They show schematically:

[0042] Fig. 1 - an ultrasonic sensor according to an embodiment in a perspective sectional view;

[0043] Fig. 2 - a sensor head board of the ultrasonic sensor equipped with electronic components in a bent state in a perspective front view;

[0044] Fig. 3 - an unpopulated sensor head board for the ultrasonic sensor in a flat state in a top view;

[0045] Fig. 4 - a circuit board panel with a plurality of unpopulated sensor head boards in a plan view; and

[0046] Fig. 5 - a simplified flow diagram of a method for manufacturing an ultrasonic sensor.

[0047] Fig. 1 shows a perspective sectional view of an ultrasonic sensor 1 with a microelectromechanical sensor unit 2. The microelectromechanical sensor unit 2 is used to generate and detect an ultrasonic signal. The ultrasonic sensor 1 can therefore be configured, for example, for a signal propagation time-based distance measurement to objects by emitting and receiving reflected ultrasonic signals. According to the exemplary embodiment shown in Fig. 1, the sensor unit 2 has two microelectromechanical sensor components 2a, which interact with membrane components 2b connected to the sensor components 2a and which can each be designed, for example, as combined transceivers in the sense of transceivers, or of which one sensor component 2a is designed as a transmitter and one sensor component 2a as a receiver.The microelectromechanical sensor components 2a have mechanical and electrical microstructures and interact with the membrane components 2b to generate and / or detect an ultrasonic signal. The membrane components 2b can, for example, be embedded in the housing base 14 or integrally connected thereto and each have a vibratable plastic membrane for ultrasound-based interaction with the environment of the ultrasonic sensor 1. The ultrasonic sensor 1 has a sensor housing 3. The sensor unit 2 and a sensor head board 6 are mechanically accommodated in the sensor housing 3 and arranged in a manner protected from environmental influences. Furthermore, according to the illustrated embodiment, the housing board 5 is also accommodated in the sensor housing 3. According to alternative embodiments, it is conceivable to arrange the housing board 5 separately from or outside the sensor housing 3.The sensor housing 3 has a housing base 14, which, according to the illustrated embodiment, has a circular basic shape. The sensor head board 6 is arranged on the housing base 14. The sensor head board 6 is spaced apart from the housing board 5 by a distance A. The microelectromechanical sensor components 2a and membrane components 2b of the microelectromechanical sensor unit 2 are embedded in the housing base 14 and are flush with an outer side of the housing base 14 facing the surroundings of the ultrasonic sensor 1.

[0048] The housing board 5 can be a substantially rigid circuit carrier, for example, a printed circuit board. According to the illustrated embodiment, the housing board 5 has a driver unit 4, which, for example, has a wiring element such as a transformer element or an inductor and a driver circuit for controlling the transformer element in order to provide the required transmission energy for generating the ultrasonic signal by means of the microelectromechanical sensor unit 2. The wiring element can also serve to control the microelectromechanical sensor unit.

[0049] A signal processing unit 7 for processing signals from the microelectromechanical sensor unit 2 is arranged on the sensor head board 6. The signal processing unit 7 forms a control circuit, embodied, for example, as an ASIC, of ​​the ultrasonic sensor 1 and can be used, among other things, to receive and evaluate sensor signals from the sensor unit 2. As can be seen in Fig. 1 and additionally in Figures 2 and 3, the sensor head board 6 has a base section 8 for receiving the signal processing unit 7 and a connecting section 9, which is integral with the base section 8, for electrically connecting the sensor head board 6 to the housing board 5. The connecting section 9 bridges the distance A between the sensor head board 6 and the housing board 5 and establishes an electrical connection between the two circuit carriers. As shown in Fig.1, the signal processing unit 7 is arranged on the base section 8 of the sensor head board 6 and electrically connected thereto, for example, by a bonding wiring not shown in detail. The base section 8 extends substantially parallel to the housing base 14, while the connecting section 9 extends substantially perpendicular to the housing base 14. The connecting section 9 is substantially strip-shaped and, according to the illustrated embodiment, protrudes substantially perpendicularly from a side edge of the base section 8.

[0050] The connecting section 9 of the sensor head board 6 has a lower flexural rigidity than the base section 8. According to the illustration shown in Figs. 1 and 2, the connecting section 9 of the exemplary embodiment is designed as a predominantly dimensionally stable connecting section 9. Thus, the connecting section 9 can be more easily elastically and / or plastically deformed than the base section 8, but experiences only a slight or insignificant recovery from its deformation when the deforming force is removed. The lower flexural rigidity is, as can be seen, for example, from Fig.2, this is already achieved geometrically by a smaller depth and width dimension of the connecting section 9 compared to the base section 8. In addition, the base section 8 can, for example, have a layer arrangement with a greater layer thickness or a higher number of layers of non-electrically conductive layers or a different material composition than the connecting section 9. As a result, the connecting section 9 is more flexible than the base section 8 and can be easily laid or guided in the sensor housing 3, while the base section 8 can have and maintain a high level of stability and a largely planar contact with the housing base 14.An ultrasonic sensor 1 according to the illustrated embodiment has a smaller number of components and reduced component complexity, particularly compared to ultrasonic sensors with separate electrical connections between the sensor head board 6 and the housing board 5. The ultrasonic sensor 1 can be manufactured simply and economically. Handling the components of the ultrasonic sensor 1 during assembly is facilitated, particularly given the limited space available. Furthermore, the quality of the electrical connection between the sensor head board 6 and the housing board 5 is improved.

[0051] Fig. 2 shows the above-described sensor head board 6 of the ultrasonic sensor 1 in a bent state in a perspective front view, in which the connecting section 9 is bent away from the base section 8. Fig. 3 shows the sensor head board 6 in a flat state, in which the connecting section 9 and the base section 8 extend in a common plane. The sensor head board 6 shown in Fig. 3 may represent an initial state of the bent sensor head board 6 shown in Fig. 2.

[0052] As can be seen in Figs. 2 and 3, the base section 8 according to the illustrated embodiment has a hexagonal outer contour 10. This allows for greater surface utilization compared to a rectangular outer contour 10, for example, particularly when using a sensor housing 3 with a housing base 14 having a circular basic shape. The additional usable surface area gained can advantageously enable or ensure an arrangement of the signal processing unit 7 on the sensor head board 6. This eliminates the need to accommodate the signal processing unit 7 on the housing board 5, so that parasitic capacitances otherwise resulting from the distance A between the sensor head board 6 and the housing board 5 can be reduced and the electromagnetic compatibility of the ultrasonic sensor 1 on the reception path can be optimized. Furthermore, Figs.2 and 3 that the base section 8 has two semicircular centering contours 8 at opposite corners of the hexagonal outer contour 10, by means of which the base section 8 can be aligned with the sensor housing 3, which has two counter-contours (not shown in detail) for engaging the centering contours 8. The centering contours 11 are designed as indentations in the present case.

[0053] Figs. 2 and 3 additionally show that, according to the illustrated embodiment, the connecting section 9 has a widening in a connection region 12 of the connecting section 9 provided for connection to the housing board 5. As can be seen in Fig. 3, a width b2 of the connection region 12 is greater than a width bi of the remaining connecting section 9 forming a coupling region 15. The connection region 12 can, for example, have a wing shape, as can be seen in Figs. 2 and 3. By widening the connecting section 9 in its connection region 12, a larger connection surface can be provided, so that the contacting of the housing board 5 in the connection region

[0054] 12 is facilitated and economical contacting methods such as hot-bar soldering processes can be used.

[0055] Fig. 4 shows a circuit board panel 13 with a plurality of sensor head circuit boards 6 in a top view. The sensor head circuit board 6 shown in Fig. 3 can, for example, be separated from such a circuit board panel 13 in order to be ready for the production of the ultrasonic sensor 1. As shown on the circuit board panel

[0056] 13, the sensor head boards 6 according to the described embodiments can be arranged next to one another in a space-saving manner due, among other things, to their hexagonal outer contours 10 and the narrower connecting sections 9 and can be removed from the board panel 13 with little waste.

[0057] Fig. 5 shows a simplified flow diagram of a method 100 for producing an ultrasonic sensor 1 with a microelectromechanical sensor unit 2. According to a first step 110 or first sub-process of the method 100, a sensor housing 3, a microelectromechanical sensor unit 2, a housing circuit board 5 and a sensor head circuit board 6 with a signal processing unit 7 are provided. The sensor head circuit board 6 can be provided, for example, by being cut out of a circuit board panel 13 shown in Fig. 4 and having a plurality of sensor head circuit boards 6. According to a second step 120 or second sub-process, a mechanical and electrical connection is established between the electromechanical sensor unit 2 and the sensor head circuit board 6. The connecting section 9 of the sensor head circuit board 6 can then be bent away from the base section 8.According to a third step 130 or third sub-process, the sensor unit 2, the sensor head board 6, and the housing board 5 are arranged in the sensor housing 3. In the third step 130, the sensor head board 6 can be integrally connected to a housing base 14 of the sensor housing 3, as shown in Fig. 1. In a fourth step 140 or fourth sub-process, an electrical connection is established between the sensor head board 6 and the housing board 5 by means of a connecting section 9 that is integrally formed with a base section 8 of the sensor head board 6 and has a lower flexural rigidity than the base section 8. To establish the electrical connection, a connecting region 12 of the connecting section 9 is connected to the housing board 5. Such a connection can advantageously be achieved, for example, by means of a bar soldering process.

Claims

Claims 1 . Ultrasonic sensor (1) with a microelectromechanical sensor unit (2) for generating and detecting an ultrasonic signal, a housing circuit board (5), a sensor housing (3) for receiving the sensor unit (2) and a sensor head circuit board (6) arranged in the sensor housing (3) and spaced apart from the housing circuit board (5) and having a signal processing unit (7) for processing signals from the microelectromechanical sensor unit (2), wherein the sensor head circuit board (6) has a base section (8) for receiving the signal processing unit (7) and a connecting section (9) formed integrally with the base section (8) for electrically connecting the sensor head circuit board (6) to the housing circuit board (5), and wherein the connecting section (9) has a lower flexural rigidity than the base section (8).

2. Ultrasonic sensor (1) according to claim 1, wherein the connecting section (9) is designed as a predominantly flexible connecting section (9).

3. Ultrasonic sensor (1) according to claim 1, wherein the connecting section (9) is designed as a predominantly dimensionally stable connecting section (9).

4. Ultrasonic sensor (1) according to one of the preceding claims, wherein the sensor head board (6) has a layer arrangement of electrically conductive and electrically non-conductive layers.

5. Ultrasonic sensor (1) according to claim 4, wherein the base portion (8) has a layer arrangement different from the connecting portion (9).

6. Ultrasonic sensor (1) according to one of the preceding claims, wherein the base portion (8) has a hexagonal outer contour (10).

7. Ultrasonic sensor (1) according to one of the preceding claims, wherein the base section (8) has a centering contour (11) for aligning the sensor head board (6) in the sensor housing (3).

8. Ultrasonic sensor (1) according to one of the preceding claims, wherein the connecting section (9) has a widening in a connection region (12) of the connecting section (9) provided for connection to the housing board (5).

9. Ultrasonic sensor (1) according to one of the preceding claims, wherein the microelectromechanical sensor unit (2) is designed as a piezoelectric ultrasonic transducer.

10. Method (100) for producing an ultrasonic sensor (1) with a microelectromechanical sensor unit (2), comprising the steps: - Providing a sensor housing (3), a microelectromechanical sensor unit (2), a housing board (5) and a sensor head board (6) with a signal processing unit (7) (110); - establishing a mechanical and electrical connection between the microelectromechanical sensor unit (2) and the sensor head board (6) (120); - arranging the sensor unit (2), the sensor head board (6) and the housing board (5) in the sensor housing (3) (130); and - Establishing an electrical connection between the sensor head board (6) and the housing board (5) by means of a connecting section (9) which is integrally formed with a base section (8) of the sensor head board (6) and which has a lower flexural rigidity than the base section (8), by connecting a connecting region (12) of the connecting section (9) to the housing board (5) (140).

11. The method according to claim 10, wherein the ultrasonic sensor (1) is designed according to one of claims 1 to 9.

12. The method according to claim 10 or 11, wherein the sensor head board (6) is provided by separating it from a board panel (13) comprising a plurality of sensor head boards (6).

13. Method according to one of claims 10 to 12, wherein before arranging the sensor head board (6) in the sensor housing (3), the connecting section (9) of the sensor head board (6) is bent from the base section (8) substantially perpendicularly or to form a C-shape or S-shape of the connecting section (9).

14. The method according to any one of claims 10 to 13, wherein the sensor head board (6) is integrally connected to a housing base (14) of the sensor housing (3) during the arrangement in the sensor housing (3).

15. The method according to any one of claims 10 to 14, wherein the connection of the connection region (12) of the connecting section (9) to the housing board (5) is carried out by means of a bar soldering process.

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