WO2023104255A1

WO2023104255A1 - Radar sensor and production method

Info

Publication number: WO2023104255A1
Application number: PCT/DE2022/200265
Authority: WO
Inventors: Xin Wang; Simon HOLZNER; Jürgen Franz; Rainer STECK
Original assignee: Continental Autonomous Mobility Germany GmbH
Priority date: 2021-12-10
Filing date: 2022-11-14
Publication date: 2023-06-15
Also published as: DE102021214166A1

Abstract

The invention relates to a radar sensor, in particular a radar sensor for object recognition for a vehicle, comprising a first circuit board having at least one high-frequency component for generating/receiving HF signals and at least one opening for in- and/or out-coupling the HF signals, and a second circuit board, wherein the first circuit board and/or second circuit board are at least partially metallised, the first circuit board and/or second circuit board have at least one recess, and the first circuit board or second circuit board has at least one opening for emitting and/or receiving the HF signals, and at least one waveguide is formed by the recess in the first circuit board and/or second circuit board and the arrangement of the circuit boards relative to one another. The invention also relates to a method for producing a radar sensor, in particular according to at least one of the preceding claims, comprising a first circuit board having at least one high-frequency component for generating/receiving HF signals and at least one opening for in- and/or out-coupling the HF signals, and a second circuit board, and a waveguide, wherein the waveguide is produced by the first circuit board and the second circuit board being arranged next to one another in such a way that the recess functions as a waveguide for the HF signals.

Description

Radar sensor and a manufacturing process

The present invention relates to a radar sensor and a production method for producing a radar sensor according to the invention.

Technological background

Modern means of transport such as motor vehicles or motorcycles are increasingly being equipped with driver assistance systems which use sensor systems to detect the environment, recognize traffic situations and support the driver, e.g. B. by a braking or steering intervention or by the output of a visual or acoustic warning. Radar sensors, lidar sensors, camera sensors or the like are regularly used as sensor systems for detecting the surroundings. From the sensor data determined by the sensors, conclusions can then be drawn about the environment. Environment detection using radar sensors is based on the emission of bundled electromagnetic waves and their reflection, e.g. B. by other road users, obstacles on the road or the edge of the road. Pedestrians are often detected using camera sensors, but radar sensors are also increasingly being used here.

Radar sensors are used for systems of the type described above, often in combination with sensors of other technologies, such as e.g. B. camera or lidar sensors. Radar sensors have i.a. the advantage that they work reliably even in poor weather conditions and, in addition to the distance from objects, can also directly measure their radial relative speed using the Doppler effect. As a rule, 24 GHz, 77 GHz and 79 GHz are used as transmission frequencies. Due to the increasing functional scope of such systems, the requirements are constantly increasing, especially with regard to the maximum detection range. At the same time, however, there is a sharp fall in prices. In addition to detecting the surroundings of motor vehicles for systems of the type described above, the interior monitoring of motor vehicles is now also coming into focus, e.g. B. to identify which seats are occupied; frequencies in the 60 GHz range are used.

A central element of every radar sensor is the antenna, which largely defines the performance and price of the radar sensor. Currently, the antennas are mostly realized in planar technology on a high-frequency circuit board, e.g. B. as patch antennas. Disadvantages of such an antenna implementation are losses in feed lines and antennas (which limits the range) and the high cost of such a circuit board, with z. B. the material and process costs are significantly higher than when using standard PCB materials.

Generic antennas usually consist (completely or partially) of a printed circuit board or PCB (Printed Circuit Board) with an etched Meta II structure in particular on an HF substrate and/or a molded part made of plastic. This can result in disadvantages such as B. high costs due to special HF substrates, fluctuating material properties or very demanding manufacturing tolerances of a molded part. In addition, the layer thickness of the surface metallization of the molded part is relatively thin (e.g. typically thinner than 5 pm, in particular including adhesion promoter, antioxidant layer, "finishing" for soldering or the like), which can affect the HF performance, the soldering quality or the like, i. H. the radar sensor works less reliably.

Printed state of the art

DE 102018203 106 A1 discloses a radar system that has one or more individual antennas for transmitting and/or receiving radar signals in order to detect the surroundings of a motor vehicle. The antenna is formed by a board and a separate molded part made of plastic (plastic antenna), the board having at least one high-frequency component and at least one opening as a coupling or decoupling point for HF signals. The molded part is made from one piece and is arranged on the opposite side of the circuit board to the at least one high-frequency component. The at least one radiating or receiving element is designed in such a way that it can receive in the direction of the circuit board or radiate from the direction of the circuit board.

Object of the present invention

Proceeding from the prior art, the object of the present invention is now to provide a radar sensor with improved performance and reliability and a manufacturing method for such a radar sensor, with which the disadvantages of the prior art are overcome in a simple and cost-effective manner. solution of the task

The above object is achieved by the entire teaching of claim 1 and the independent claim. Expedient developments of the invention are claimed in the dependent claims.

The radar sensor according to the invention is used in particular for object recognition and can be used practically in the automotive or vehicle sector. The radar sensor comprises a first circuit board with at least one HF component or high-frequency component for generating and/or receiving HF signals (or radar signals) and at least one opening for coupling and/or decoupling the HF signals, and a second Circuit board, wherein the first circuit board and second circuit board are at least partially metallized, the first circuit board and/or second circuit board have at least one, in particular longitudinal, recess, and the first circuit board or the second circuit board has at least one opening for radiating and/or receiving the RF -Has signals. Furthermore, at least one waveguide is formed by the recess or the recesses in the first circuit board and/or the second circuit board and the arrangement of the circuit boards relative to one another, d. H. the waveguide is created by the space, in particular air-filled, within the recess(es) which is created by the metalized wall of the recess in the first and/or second circuit board. The special arrangement of the circuit boards and the recess(es) therein results in a waveguide antenna or a waveguide slot antenna, which includes the recess and the opening for radiating and/or receiving the HF signals.

The printed circuit boards of the radar sensor according to the invention preferably contain no HF substrate. Due to the fact that an HF substrate does not necessarily have to be used for the printed circuit boards, the radar sensor according to the invention can be produced particularly cost-effectively with little outlay in terms of production and time. Furthermore, the recesses can also be produced in a simple manner during the production process of the circuit board, as a result of which the expenditure of time and money is reduced to a particular extent. In addition, the circuit board can thus fulfill mechanical as well as electromagnetic functions.

An HF substrate within the meaning of the invention is understood to be a substrate that has constant parameters that are specifically optimized for use in the high-frequency range. These parameters include a constant permittivity and the smallest possible loss angle. The value of the loss angle of common RF substrates is typically 0.005 or less at 10 GHz. All types of printed circuit boards are included as circuit boards within the meaning of the invention, e.g. As circuit boards or printed circuits (PCB, Printed Circuit Board), which are used as a carrier for electronic components. The printed circuit boards comprise an electrically insulating material and, as a rule, conductive connections (so-called conductor tracks) adhering thereto. As an insulating material z. B. fiber-reinforced plastic or laminated paper (especially from phenolic: fiber composite material made of paper and phenol-formaldehyde resin) can be used. The conductor tracks are usually etched from a thin layer of copper with a thickness in the range of e.g. B. 10-50 pm. Components can then be soldered on soldering surfaces (pads) or in soldering eyes, e.g. B. microchips, HF chips or HF components, transmitting and receiving antennas. The circuit board types range from single-sided circuit boards to multilayer and special technologies. All types and/or materials of circuit boards known from the prior art can be used as circuit boards, such as e.g. B. Standard printed circuit boards, single-sided and double-sided printed circuit boards, multilayer boards with several layers, Flexlam, thin printed circuit boards, thick copper printed circuit boards, coated printed circuit boards, printed circuit boards on glass, HDI (high-density interconnect) printed circuit boards, SBU (sequential build up) printed circuit boards, LBA (conductor pattern -Construction) circuit boards, IMS (Insulated Metal Substrate) circuit boards or the like. By selecting a lossy circuit board material, unwanted substrate waves can be suppressed, resulting in fewer disturbances in the area of the antenna or in the directivity pattern. Furthermore, the “CTE mismatch” in the radar sensor can be well balanced through a suitable selection of circuit board substrates or materials; in particular, the first and second circuit boards can be made of the same or different material. According to a preferred embodiment of the invention, at least one of the circuit boards may comprise a fire resistant material and/or a bismaleimide trizine resin and/or a polyimide material and/or an epoxy matrix material and/or the like, the loss angles of these materials should be greater than 0.005 at 10 GHz.

The first circuit board and the two circuit boards can expediently be connected to one another via soldering points (e.g. solder balls or solder drops, in particular precisely defined by a so-called solder mask), i. H. they are connected to each other by a soldering process. In particular, with a standard solder mask, the soldering quality, e.g. B. in terms of soldering width and height, easily controlled and improved.

Alternatively or additionally, the first circuit board and the two circuit boards can also be connected to one another by means of gluing, pressing, pressing together or the like, The recesses or the wall of the recess or also the circuit boards are preferably at least partially metallized. This results in the advantage that the metal layer of the in particular milled waveguide antenna is more massive or thicker than conventional layers of the molded part applied by means of PVD processes and is easier to produce and implement.

Furthermore, the waveguide antenna or the waveguide can be formed or arranged on the side of the first board facing the at least one high-frequency component or on the opposite side, with the at least one radiating or receiving element radiating in the direction of the second board (or to the antenna) or from the direction of the second circuit board (or from the direction of the antenna). The invention thus explicitly includes all configurations in which the antenna is arranged either in the direction of the HF component or in the opposite direction.

The present invention also claims a method for producing a radar sensor, which comprises a first circuit board with at least one high-frequency component for generating/receiving HF signals and a second circuit board, the first circuit board and/or second circuit board preferably being at least partially metalized. At least one recess is created in the first and/or second circuit board and an opening for coupling and/or decoupling the HF signals in the first circuit board, and at least one opening for radiating and/or receiving the HF signals in the first circuit board or the second circuit board is generated. In addition, a waveguide is produced by arranging the first circuit board and the second circuit board on one another in such a way that the recess serves as a waveguide for the HF signals. Advantageously, the waveguide antenna or the waveguide, which is created by the special arrangement of the circuit boards and the recess, does not have to be provided as a separate component, but is provided in a simple and inexpensive manner by the arrangement of the circuit boards and the recesses in the circuit board(s). formed during the manufacturing process.

In a preferred embodiment of the method, this has the following method steps:

providing a first circuit board and a second circuit board,

Creating a recess in the first circuit board and/or second circuit board, and creating an opening for coupling and/or decoupling the HF signals in the first circuit board, and

creating an opening for radiating and/or receiving the RF signals in the first circuit board or the second circuit board, and arranging the first circuit board and the second circuit board together.

Alternatively, however, the arrangement of an HF component on the first circuit board is preferred (this can be attached by soldering, for example),

In particular, the order of the method steps can vary, for example by creating the openings for coupling and/or coupling out the HF signals and the openings for emitting and/or receiving recesses for the HF signals in parallel (e.g. by depth milling) or one after the other become. Or that the RF component is attached to the first board before or after the assembly of the two boards.

The at least one recess can expediently be produced by milling, in particular controlled depth milling. This technique offers the advantage that the recesses can be produced particularly easily, inexpensively and quickly. The recesses can be designed in the form of slots, tubes, round and/or rectangular channels.

The openings can expediently be produced by means of controlled depth milling, drilling and/or laser technology.

Furthermore, the first circuit board and the second circuit board can be connected to each other by soldering.

A solder mask can advantageously be used for the soldering, with several soldering points being provided at definable locations in order to improve the connection process and the later connection to a particular extent. The term "solder mask" within the meaning of the invention includes in particular all known configurations such as solder resist, solder resist, solder mask or resist.

Alternatively or additionally, the first circuit board and the second circuit board can also be connected to one another (in particular by means of conductive material) by (low-temperature) sintering and/or welding and/or pressing together and/or gluing.

The method can preferably have the method step of metallizing or partially metallizing the recesses. In a practical manner, the recess(es) for the waveguide are first produced on the circuit board, followed by the openings and then, after the mechanical work, the metallization. The assembly The circuit board with the HF component (e.g. MMIC - Monolithic Microwave Integrated Circuit) can then optionally take place as a step after the production of the first circuit board, but also after the circuit boards have been connected or soldered/glued together.

In the following, the invention is described in more detail with reference to expedient exemplary embodiments. Show it:

1 is a simplified schematic of a prior art radio frequency board of a radar system;

2 shows a simplified schematic representation of an embodiment of a radar sensor according to the invention;

3 shows a simplified schematic illustration of a further embodiment of a radar sensor according to the invention;

4 shows a simplified schematic illustration of a further embodiment of a radar sensor according to the invention;

5 shows a simplified schematic representation of a further embodiment of a radar sensor according to the invention, and

6 shows a simplified illustration of an embodiment of the production method according to the invention.

Generic antennas for radar systems for detecting the surroundings are usually implemented as planar antennas on a high-frequency circuit board. 1 shows a high-frequency circuit board with a high-frequency component, a so-called MMIC (Monolithic Microwave Integrated Circuit) and with three transmitting antennas (TX) and four receiving antennas (RX), the antennas each being composed of several individual radiators. The antennas are implemented as planar patch antennas.

The antennas and their leads from the high-frequency chip require a special substrate on the top layer of the high-frequency circuit board with material data suitable for high-frequency (e.g. defined thickness, defined dielectric constant, very low loss angle). In particular, the material costs of this special substrate and its processing (also because of the required high level of structural accuracy) result in costs that are higher by a factor of a factor compared to a purely low-frequency circuit board of the same size and the same number of layers. In addition to the costs, however, the signal losses in the antennas and their feed lines are also disadvantageous.

2 shows an embodiment of the radar sensor 1 according to the invention or a sensor device. The radar sensor 1 comprises a first circuit board 2 and a second circuit board 3. The first circuit board 2 has a metallization 2a on its surface and an HF component 4 attached thereto for transmitting HF signals or radar signals. The HF component 4 is fastened to the circuit board 2 via solder balls 8 . The second circuit board 3 also has a metallization 3a. The metallization 2a, 3a in FIG. 2 is continuous, but the invention also explicitly includes configurations of the radar sensor 1 in which the metallization 2a, 3a is not implemented circumferentially but only partially on the circuit boards 2, 3. The circuit boards 2, 3 are arranged on one another and connected to one another in a simple manner, for example by soldering them to one another. For the soldering process, the circuit board 3 has a solder mask 10, which is used to hold the solder 9, so that the soldered connection takes place at points that are to be defined. However, the connection also explicitly includes configurations in which the solder mask is not only provided on one of the circuit boards 2, 3, but rather a solder mask 10 is located on both circuit boards 2, 3. Furthermore, the first circuit board 2 includes an opening 5 for coupling and/or coupling out the HF signals. In addition, the second circuit board 3 has a recess 6, which has preferably been produced using controlled depth milling technology and serves as a waveguide, the HF signals can thus be generated in the HF component 4, through the opening 5 in the waveguide or the recess 6 are coupled in, passed on through them and finally radiated through the opening 7 . In the same way, radar signals or HF signals can also be received through the opening 7 , guided through the waveguide or the recess 6 to the opening 5 and finally coupled out through the opening 5 to the HF component 4 . The waveguide antenna of the radar sensor 2 is formed here by the space created by the recess 6 and the adjacent conversions of the circuit boards 2, 3, and the opening 7 for emitting/receiving HF signals.

3 shows a further embodiment of a radar sensor 1 according to the invention. In contrast to the embodiment according to FIG. 2, the first printed circuit board 2, which includes the HF component 4, has not only the opening 5 for coupling the radar signals in or out, but also the recess 6 and the opening 7 for radiating and/or receiving the HF signals. signals up. The circuit board 3 serves only to delimit the space that is created by the recess 6 . The circuit boards 2, 3 are in this case also arranged on one another or connected to one another via solders or solder 9, which are applied in solder masks 10 arranged on both sides of each of the circuit boards 2, 3.

4 shows a further embodiment of a radar sensor 1 according to the invention. In contrast to the embodiment according to FIG. 3, the first circuit board 2 and the second circuit board 3 each have a recess 6a, 6b, d. H. the recesses 6a, 6b thus form a common recess 6, which is used for wave guidance. According to FIG. 4, the radar signals or HF signals are emitted starting from the HF component 4 through the opening 5, the space formed by the recesses 6a, 6b, and the opening 7d. H. against the emission direction of the HF component 4.

A further embodiment of a radar sensor 1 according to the invention is shown in FIG. 5 . In contrast to the embodiment according to FIG. 4, the opening 7 for emitting and/or receiving the HF signals is not in the first circuit board 2, but in the second circuit board 3. According to FIG. 5, the radar signals are emitted starting from the HF Component 4 through the opening 5, the space formed by the recesses 6a, 6b, and the opening 7, i. H. in the same emission direction of the HF component 4.

FIG. 6 shows an embodiment of a method sequence according to the invention for producing a radar sensor. Providing (step I) a first circuit board 2 and a second circuit board 3. Creating at least one recess 6, 6a, 6b on the first circuit board 2 and/or the second circuit board 3 (step II), preferably several longitudinal or slotted , Tubular or rectangular recesses 6, 6a, 6b are produced on/in the first circuit board 2 and/or the second circuit board 3 by means of depth milling technology. This is followed by the following method steps: creating a first opening 5 for coupling and/or decoupling the HF signals in the first circuit board (step III) and creating a second opening 7 for radiating and/or receiving the HF signals in the first circuit board or the second board (Step IV). Thereafter, the circuit boards 2, 3--alternatively only the walls of the recess(es) 6, 6a, 6b--and the walls of the openings 5, 7 are metallized (step V). Furthermore, a high-frequency component or HF component 4 can be arranged on the first circuit board 1 (step VI), in that it is preferably connected to the first circuit board 2 via solder balls 8 . Subsequently, the waveguide or the waveguide antenna is produced or manufactured by arranging the first circuit board 2 and the second circuit board 3 on one another (step VII) and connecting them (step VIII), e.g. B. through Soldering. The order of the process steps (steps II-VIII) can be specified explicitly according to the best possible process flow.

According to another embodiment of the process sequence, the production process could include the steps of selective etching, application of the solder mask 10 and finishing of the surface after the provision (step I), the mechanical processing according to steps II-IV and the subsequent metallization (step V), before then the assembly (e.g. with the HF component according to step VI) and the arranging (according to step VII or step VII and step VIII) takes place.

REFERENCE LIST

1 radar sensor

2 first circuit board

2a metallization

3 circuit board

3a metallization

4 RF component

5 opening

6 recess

6a recess

6b recess

7 opening

8 solder bead

9 lot

10 Solder Mask

Claims

PATENT CLAIMS

1. Radar sensor (1), in particular for object detection for a vehicle, having a first circuit board (2) with at least one high-frequency component (4) for generating/receiving HF signals and at least one opening (5) for coupling and/or decoupling of the HF signals, and a second circuit board (3), the first circuit board (2) and/or second circuit board (3) being at least partially metalized, the first circuit board (2) and/or second circuit board (3) having at least one recess (6, 6a, 6b), and the first circuit board (2) or second circuit board (3) has at least one opening (7) for radiating and/or receiving the HF signals, and a waveguide through the recess (6, 6a , 6b) in the first circuit board (2) and/or second circuit board (3) and the arrangement of the circuit boards (2, 3) relative to each other.

2. Radar sensor (1) according to claim 1, characterized in that the first circuit board (2) and the second circuit board (3) are connected to one another via soldering points (9).

3. Radar sensor (1) according to claim 1 or 2, characterized in that the first circuit board (2) and the second circuit board (3) are connected via mechanical pressure and / or gluing.

4. Radar sensor (1) according to any one of the preceding claims, characterized in that the recess (6, 6a, 6b) is at least partially metallized.

5. Radar sensor (1) according to any one of the preceding claims, characterized in that the first board (2) and / or second board (3) are at least partially metallized.

6. Radar sensor (1) according to one of the preceding claims, characterized in that at least one of the circuit boards (2, 3) comprises a fire-resistant material and/or a bismaleimide trizine resin and/or a polyimide material and/or an epoxy matrix material and/or the like.

7. Radar sensor (1) according to any one of the preceding claims, characterized in that a solder mask (10) is provided on at least one of the circuit boards (2, 3).

8. Radar sensor (1) according to one of the preceding claims, characterized in that the waveguide is formed on the opposite side of the high-frequency component of the first circuit board (1).

9. Method for producing a radar sensor (1), in particular according to at least one of the preceding claims, comprising a first circuit board (2) with at least one high-frequency component (4) for generating/receiving HF signals, and a second circuit board (3), wherein at least one recess (6, 6a, 6b) is produced in the first circuit board (2) and/or in the second circuit board (3), at least one opening (5) for coupling and/or decoupling the HF signals in the first circuit board (2) is produced, and at least one opening (7) for radiating and/or receiving the HF signals is produced in the first circuit board (2) or the second circuit board (3), and a waveguide is produced by the the first circuit board (2) and the second circuit board (3) are arranged next to one another in such a way that the recess (6, 6a, 6b) serves as a waveguide for the HF signals.

10. The method according to claim 9, characterized in that the method has the following method steps:

- Providing a first circuit board (2) and a second circuit board (3),

- Creating a recess (6, 6a, 6b) in the first circuit board (2) and/or second circuit board (3), and

- Creating an opening (5) for coupling and/or decoupling the HF signals in the first circuit board (2),

- Creating an opening (7) for radiating and/or receiving the HF

Signals in the first board (2) or the second board (3), and

- Arranging the first circuit board (2) and the second circuit board (3) together.

11. The method according to claim 9 or 10, characterized in that the at least one recess (6, 6a, 6b) is produced by controlled depth milling. 14

12. The method according to any one of claims 9 to 11, characterized in that the openings (5, 7) are produced by means of controlled depth milling and/or drilling and/or laser technology.

13. The method according to any one of claims 9 to 12, characterized in that the first circuit board (2) and the second circuit board (3) are connected to one another by soldering.

14. The method according to claim 13, characterized in that a solder mask (10) is used for the soldering.

15. The method according to any one of claims 9 to 14, characterized in that the first circuit board (2) and the second circuit board (3) are connected to one another by (low-temperature) sintering and/or welding and/or pressing together and/or gluing.

16. The method according to any one of claims 9 to 15, characterized in that the method further comprises the following method step:

- Metallization or partial metallization of the circuit boards (2, 3) and/or the recess (6, 6a, 6b).