Hollow waveguide element and method for producing same

Abstract

The invention relates to a hollow waveguide element comprising a channel (10) which has an open side that is delimited by at least one lateral wall (11, 12). The lateral wall (11, 12) has multiple mutually separate electrical contact surfaces (20).

Description

[0001] Description

[0002] title

[0003] Waveguide element and method for its manufacture

[0004] The present invention relates to a waveguide element, in particular for a radar sensor. Furthermore, the present invention relates to a method for producing the waveguide element.

[0005] State of the art

[0006] Radar sensors are used in vehicles to implement comfort and safety features. They directly measure the distance to a target without relying on image interpretation, as is the case with an optical camera, for example.

[0007] Antenna structures for radar sensors can be designed as planar antennas on a circuit board, particularly as microstrip antennas. Three-dimensional waveguide antennas are also used. These exhibit lower power loss and higher broadband performance compared to planar antennas. Waveguide antennas typically consist of several layers that must be glued or soldered together.

[0008] DE 10 2020 216 362 A1 describes a radar sensor with a waveguide structure in the form of a channel open on one side. This channel is soldered with its open side to a copper layer of a circuit board, so that the copper layer forms one wall of the waveguide.

[0009] Disclosure of the invention The waveguide element is particularly designed to guide an electromagnetic wave with a wavelength X. It has a channel with an open side that is delimited by at least one side wall. For example, the channel can have a single side wall that completely surrounds it or it can have multiple side walls. In addition to the side wall that delimits the open side or the side walls that delimit the open side, it can in particular have at least one wall opposite the open side that is connected to the side wall or the side walls. The at least one side wall has a plurality of separate electrical contact surfaces. An electrical contact surface is understood to mean a surface that is provided and designed to solder or electrically conductively bond the side wall of the channel to a metal surface.This metal surface is, in particular, a metallic base surface of a circuit board. The open side can thus be closed by means of the metal surface. In one embodiment of the waveguide element, the channel can also be made of a metal. In another embodiment of the waveguide element, it consists of a carrier material, such as a plastic, which has a metallization layer on the inside of the channel.

[0010] In principle, it is possible to solder or glue the side walls of such a channel to a metal surface across their entire surface. However, such a full-surface connection would create a rigid connection between the waveguide element and the metal surface, which carries a high risk of bending and breakage over the lifetime of the waveguide element. It has been found that this risk can be reduced by using several separate electrical contact surfaces.

[0011] The length and / or width of each electrical contact surface is preferably in the range of 0.3 mm to 1.5 mm. The area of ​​each electrical contact surface is preferably in the range of 0.09 mm 2 up to 2.25 mm 2Such electrical contact surfaces have the advantage that, on the one hand, they guarantee a resilient connection between the channel and the metal surface and, on the other hand, they keep the contact area between the channel and the metal surface so small that the waveguide element has a high tolerance to mechanical stress.

[0012] The distance between two adjacent electrical contact surfaces is preferably in the range from 0.3 mm to λ / 4, and is particularly preferably less than λ / 8. The height of the openings between the contact surfaces is also preferably in the range from 0.3 mm to λ / 4, and is particularly preferably less than λ / 8 in order to minimize the influence on wave propagation. As a result, the electrical contact surfaces are, on the one hand, close enough to reliably connect the waveguide element to the metal surface, and, on the other hand, far enough apart to significantly reduce the sensitivity of the waveguide element to mechanical stress.

[0013] The electrical contact surfaces are preferably separated by means of openings through a sidewall, which can be, in particular, round-arched or rectangular. Such openings cause unopened regions of the sidewall, each of which ends in an electrical contact surface, to take the form of pins, which are well suited for a defined point-by-point connection between the channel and a metal surface. At the same time, it has been found that such openings do not negatively affect the waveguide properties of the channel. The openings can, in particular, be designed as serrations in the sidewalls.

[0014] The channel preferably has a rectangular cross-section, which makes it easy to manufacture. Its height from the open side to the side of the channel opposite this open side is preferably in the range of λ / 2 to X, as this represents a monomodal rectangular waveguide.

[0015] The channel is preferably arranged on a metallic base surface of a printed circuit board, the outer contour of which corresponds to the outer contour of the open side of the channel. This metallic base surface, which is particularly made of copper, can also be referred to as a footprint. If the electrical contact surfaces are separated by means of openings through the side wall, the outer contour of the metallic base surface has a toothed structure, which facilitates precise positioning of the channel on the printed circuit board. The electrical contact surfaces of the channel are soldered or glued to the teeth protruding in the outer contour of the metallic base surface.

[0016] One wall of the channel, opposite its open side, is extended beyond the channel's cross-section and can function as an antenna structure for a radar sensor. One or more openings extend through this wall into the channel's interior and can serve as radiating elements for a radar wave.

[0017] The circuit board preferably further comprises a circuit with integrated microwave conductors (Monolithic Microwave Integrated Circuit; MMIC) for a radar sensor, which is wave-guidedly connected to the channel. This circuit can be arranged on the same side of the circuit board as the channel to protect it from heat and parasitic radiation below the side of the channel extended into an antenna structure, or it can be arranged on the side of the circuit board facing away from the channel, with the wave-guided connection extending through the circuit board.

[0018] In a method for producing such a waveguide element having a printed circuit board, a waveguide element is first provided which only has the channel open on one side. Furthermore, a printed circuit board with a metallic base surface is provided, the outer contour of which corresponds to the outer contour of the open side of the channel of the waveguide element. The channel is then attached to the metallic base surface of the printed circuit board at the electrical contact points by soldering or electrically conductive bonding, in order to obtain a waveguide element which is delimited on one side by the metallic base surface of the printed circuit board and on its other sides by the walls of the channel. The surface tension effects of the solder paste or adhesive ensure precise alignment of the channel on the metallic base surface.

[0019] Brief description of the drawings Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

[0020] Figure 1 shows an isometric view of a waveguide element according to an embodiment of the invention.

[0021] Figure 2 shows an isometric view of a waveguide element according to another embodiment of the invention.

[0022] Figure 3a shows an isometric view of a channel of a waveguide element according to yet another embodiment of the invention.

[0023] Figure 3b shows a top view of the channel according to Figure 3a.

[0024] Figure 4 shows a plan view of a circuit board which, in one embodiment of the invention, can be connected to a channel made of a waveguide element.

[0025] Figure 5 shows an isometric view of the channel according to Figures 3a and 3b, the open side of which has been largely closed by a metallic base surface of a circuit board.

[0026] Figure 6 shows an isometric view of a waveguide element according to an embodiment of the invention, which has the channel according to Figures 3a and 3b and the circuit board according to Figure 4.

[0027] Figure 6b shows a sectional side view of the waveguide element according to Figure 6a.

[0028] Figure 7 shows a flowchart of a method for producing a waveguide element according to an embodiment of the invention.

[0029] Embodiments of the invention A waveguide element according to a first embodiment of the invention is shown in Figure 1. This has a channel 10 with a rectangular cross-section. The channel 10 has two side walls 11, 12, each of which has electrical contact surfaces 20 on its underside. The side walls 11, 12 have semi-circular openings 21, which form the electrical contact surfaces

[0030] 20 from each other. The channel 10 is arranged on a printed circuit board 30 such that the electrical contact surfaces 20 are soldered to a metallic base surface 31 of the printed circuit board 30, which is made of copper. The metallic base surface 31 forms the underside of the channel 10. Its three other sides are formed by metallization on the inner walls of the channel 10.

[0031] Figure 2 shows a second embodiment of the waveguide element according to the invention. This differs from the first embodiment in the dimensions of the channel 10. While in the first embodiment, the width of the channel 10 is greater than its height, in the second embodiment, the height of the channel 10 is greater than its width. In both embodiments, the outer contour of the metallic base surface corresponds exactly to the outer contour of the open side of the channel 10, which is delimited by the two side walls 11, 12.

[0032] The channel 10 of a waveguide element according to a third embodiment of the invention is shown in Figures 3a and 3b. This channel 10 is T-shaped and is delimited by a single circumferential side wall 13. This side wall 13 has semi-circular openings similar to the side walls 11, 12 in the first two embodiments.

[0033] 21 and is therefore toothed. The areas of the side wall 13 remaining between the openings 21 each end in electrical contact surfaces 20. A wall of the channel 10 designed as an antenna surface 14 lies opposite its open side and extends beyond the cross-section of the channel 10. Four radiation openings 15 break through the antenna surface 14 and thus connect the channel 10 in a wave-guiding manner to the side of the antenna surface 14 opposite the channel 10. The channel 10 according to the third exemplary embodiment of the invention is intended to be soldered to a printed circuit board 30, which is shown in Figure 4. This has a metallic base surface 31 made of copper, which has a toothed outer contour that corresponds to the toothed contour of the side wall 13 of the channel 10. A waveguiding via 32 extends from the metallic base surface 31 through the circuit board 30 to its opposite side.The inner walls of via 32 are metallized.

[0034] If the channel 10 is soldered onto the metallic base surface 31, the result is a structure shown in Figure 5 with the remaining circuit board 30 omitted. The complete waveguide element obtained in this way is shown in Figures 6a and 6b. On the side of the circuit board 30 facing away from the channel 10, an MMIC is connected by means of a ball grid array 41 (BGA). This is configured to function as a transceiver for a radar sensor. Radar waves are guided from the MMIC 40 through the via 32 and the channel 10 to the radiating elements 15 and radiated by the radar sensor. Such a radar sensor can be used in particular in a motor vehicle.

[0035] The sequence of a manufacturing method for a radar sensor according to the third exemplary embodiment of the invention is shown schematically in Figure 7. After the start 50 of the method, the still unfinished waveguide element, which consists only of the channel 10 according to Figures 3a and 3b, is first provided. This is followed by the provision 52 of the printed circuit board 30 according to Figure 4. The electrical contact surfaces 20 of the side wall 13 of the channel 10 are provided with a solder paste, positioned precisely on the metallic base surface 31 of the printed circuit board 30, and then fastened thereto by soldering 53. The surface tension of the solder paste guarantees correct positioning of the channel 10. The method is then terminated 54. The arrangement of further electronic components, such as the MMIC 40 on the printed circuit board 30, can take place before or after these method steps 50 to 54.

Claims

Claims 1 . Waveguide element comprising a channel (10) with an open side which is delimited by at least one side wall (11 - 13), characterized in that the side wall (11 - 13) has a plurality of separate electrical contact surfaces (20) 2. Waveguide element according to claim 1, characterized in that a height and / or width of each contact surface (20) is in the range of 0.3 mm to 1.5 mm.

3. Waveguide element according to claim 1 or 2, characterized in that a distance between two adjacent contact surfaces (20) is in the range of 0.3 mm to λ / 4 mm, where X is a wavelength of an electromagnetic wave for which the waveguide element is designed 4. Waveguide element according to one of claims 1 to 3, characterized in that the separation of the contact surfaces (20) is effected by means of openings (21) through the side wall (11 - 13) 5. Waveguide element according to claim 4, characterized in that the openings (21) are round-arched or rectangular.

6. Waveguide element according to claim 4 or 5, characterized in that the openings (21) are designed as teeth of the side wall (11 - 13).

7. Waveguide element according to one of claims 1 to 6, characterized in that the channel (10) has a rectangular cross-section.

8. Waveguide element according to one of claims 1 to 7, characterized in that the channel (10) is arranged on a metallic base surface (31) of a printed circuit board (30), the outer contour of which corresponds to the outer contour of the open side of the channel (10).

9. Waveguide element according to claim 8, characterized in that the printed circuit board (30) has an MM IC (40) for a radar sensor, which is wave-conductingly connected to the channel (10) 10. A method for producing a waveguide element according to claim 8 or 9, comprising the following steps: Providing (51) a waveguide element according to one of claims 1 to 7, providing (52) a printed circuit board (30) with a metallic base surface (31), the outer contour of which corresponds to the outer contour of the open side of the channel (10) of the waveguide element, and Fastening (53) the channel (10) to the contact surfaces (20) on the metallic base surface (31) by means of soldering or electrically conductive bonding.

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