High frequency circuit with circuit board and waveguide structure

Abstract

A high-frequency circuit having a circuit board (10) which carries at least one electronic component (16, 16') and a conductor structure (14), and having a waveguide structure (12) which is manufactured separately from the circuit board, the waveguide structure being arranged on the circuit board (10) in such a way that high-frequency signals can be transmitted between the conductor structure (14) on the circuit board and the waveguide structure (12), characterized in that the waveguide structure (12) is held on the circuit board (10) by means of press-in pins (34).

Description

Technical Field

[0001] The present invention relates to a high-frequency circuit having a circuit board carrying at least one electronic component and a conductor structure, and having a waveguide structure manufactured separately from the circuit board, the waveguide structure being disposed on the circuit board such that high-frequency signals can be transmitted between the conductor structure and the waveguide structure on the circuit board.

[0002] The present invention relates in particular to a high-frequency circuit for a portion of a radar sensor used in motor vehicles. Background Technology

[0003] In motor vehicles, radar sensors are used in conjunction with driver assistance or safety systems (such as systems for electronic distance adjustment or collision warning) to detect the traffic environment. To obtain the most complete possible picture of the traffic conditions, the radar sensor should have a wide detection range, especially in the azimuth angle. For this purpose, radar sensors are typically used that have a high-frequency circuit of the type described above, and in which a waveguide structure forms a waveguide antenna by means of which radar signals are transmitted and / or received.

[0004] The conductive structures on the circuit board form feed points (Einspeisungsstellen), the so-called transmitters. Through these transmitters, high-frequency signals can be coupled into the waveguide structure, or conversely, received radar signals can be coupled into the conductive structure and transmitted to the electronic components for signal analysis and processing. For fault-free signal transmission, very precise positioning of the waveguide structure relative to the transmitters is crucial.

[0005] In several conventional high-frequency circuits of this type, waveguide structures (e.g., molded parts made of plastic with metallized walls) are held on the circuit board by means of screw connections. A disadvantage here is that the heads of the fixing screws occupy a relatively large area on the side of the circuit board away from the waveguide structure, which is then no longer available for electronic components and printed conductors.

[0006] One known alternative is to use adhesive bonding instead of screws. While this reduces space consumption on the circuit board, the manufacturing process becomes more complex, primarily because the adhesive must cure at high temperatures. This requires a heated chamber where high-frequency circuitry has a relatively long dwell time, thus making high manufacturing yields only achievable with high facility costs. Summary of the Invention

[0007] The objective of this invention is to enable precise placement and reliable fixation of waveguide structures on circuit boards with low manufacturing costs.

[0008] According to the present invention, this task is solved by holding the waveguide structure on the circuit board by means of press-in pins.

[0009] The press-fit technique using press-fit pins has been successfully used to manufacture electrical connections between conductor boards and electrical plugs. If this technique is used to mount waveguide structures on a circuit board, the position of the waveguide structure relative to the transmitter is predefined by the position of a press-fit sleeve formed in the circuit board. Then, press-fit pins arranged on the waveguide structure are precisely pressed into the press-fit sleeve. Reliable retention of the waveguide structure on the circuit board is achieved through the force-locking (Kraftschluss) of the press-fit pins in the sleeve and, where necessary, through a diffusion process that creates an intermetallic connection between the press-fit pins and the metal lining of the sleeve, without the need for time-consuming and expensive methods of hardening adhesives.

[0010] The present invention provides a high-frequency circuit having a circuit board carrying at least one electronic component and a conductor structure, and having a waveguide structure manufactured separately from the circuit board, the waveguide structure being arranged on the circuit board such that high-frequency signals can be transmitted between the conductor structure and the waveguide structure on the circuit board, wherein the waveguide structure is held on the circuit board by means of a push-in pin.

[0011] Advantageous configurations and extensions of the invention are described below.

[0012] In one implementation, the waveguide structure is a molded body made of plastic. The waveguide structure is formed in such a way that the channels correspond to the desired orientation of the waveguide segments. These channels are open to the surface of the molded body, allowing for easy demolding during the fabrication of the molded body. To form the waveguide structure, the walls of the channels are metallized, and the channels are closed on the open side by a sheet of metal (Blechplatte). The press-in pins can then be easily manufactured by stamping elongated strips from the sheet of metal and bending them at right angles, wherein the thickness of the sheet of metal and the width of the strip are chosen to match the dimensions of the press-in sleeves in the circuit board.

[0013] The metal plate forming the press-in pins can be located on the side of the waveguide structure facing the circuit board, or alternatively, on the side facing away from the circuit board. In the latter case, the waveguide structure can form several through-holes (Durchbrüche) in the press-in pins, thereby achieving the most uniform possible distribution of the press-in pins on the surface of the circuit board.

[0014] Waveguide structures typically form a coupling dome with a coupling channel that extends perpendicularly to the plane of the circuit board and opens toward the transmitter on the board. In one embodiment, a press-in pin is pressed so deeply into a sleeve within the circuit board that the coupling dome is integrally attached to the board. In this way, dimensional tolerances are minimized.

[0015] Besides the mechanical fixing and mounting functions of the waveguide structure, the metal sheet forming the press-in pin can also take on other functions. For example, the metal sheet can be part of the EMV shielding for electronic components on a circuit board. Furthermore, due to its good thermal conductivity, the metal sheet can also be used for heat dissipation in electronic components.

[0016] The transmitter on the circuit board can be surrounded by a conductive layer, through which the air gap between the circuit board and the coupling dome is completely electrically sealed. Alternatively, the conductive layer can also be formed of a conductive adhesive, which also helps to mechanically fix the waveguide structure on the circuit board.

[0017] In another embodiment, the circuit board can be elastically preloaded against the top of the coupling dome, especially in the area of ​​the coupling dome. Attached Figure Description

[0018] The embodiments are described in detail below based on the accompanying drawings.

[0019] The attached diagram shows:

[0020] Figure 1 A perspective, partially exploded view of a high-frequency circuit according to an embodiment of the present invention is shown;

[0021] Figure 2 A cross-sectional view of a high-frequency circuit according to an embodiment of the present invention is shown;

[0022] Figures 3 to 5 A cross-sectional view of a high-frequency circuit according to another embodiment of the present invention is shown;

[0023] Figure 6 Shown from top view according to Figure 5 High-frequency circuits;

[0024] Figure 7 and Figure 8 A cross-sectional view of a high-frequency circuit according to another embodiment of the present invention is shown;

[0025] Figure 9 Shown from top view according to Figure 8 High-frequency circuits. Detailed Implementation

[0026] Figure 1An example of a high-frequency circuit with a circuit board 10 and a waveguide structure 12 is shown, in which a waveguide antenna for a radar sensor is formed. The circuit board 10 carries an electrical conductor structure 14 (e.g., a microstrip line) and at least one electronic component 16 (e.g., a monolithic microwave integrated circuit) on its surface for generating a frequency-modulated radar signal that is then transmitted through the waveguide antenna, and for receiving and further processing radar echoes from a located object.

[0027] Waveguide structure 12 is formed from a block of plastic, which forms channels 18, 20 with metallized sidewalls. These channels are surrounded by conductive surfaces on their entire periphery and serve as waveguides for further transmission of microwave signals. Figure 1 In the example shown, the depth of channels 18 and 20 is less than the thickness of the plastic block, and the bottoms of channels 18 and 20 are formed by the metallized walls of the plastic block, respectively. On the upper side, channels 18 and 20 are closed by a metal sheet 22, in which a radiation opening 24 for emitting microwave radiation is formed at a defined location on the waveguide.

[0028] A plastic block 12 of the waveguide structure forms a coupling dome 26 at a defined location. This coupling dome protrudes in the direction of the circuit board 10 and defines vertical coupling channels 28, which are part of the waveguide network. On the circuit board 10, a so-called transmitter 30 is formed within the cross-section of the coupling channel 28 and precisely centered on the coupling channel (see [link to circuit board 10]). Figure 2 The transmitter is connected to the component 16 via the conductor structure 14, and the microwave signal generated in the component 16 is coupled into the waveguide antenna via the transmitter.

[0029] exist Figure 1 In this arrangement, a plastic block forming the waveguide structure 12 is fixedly arranged on a lower metal plate 32, which is secured to the circuit board 10 in one aspect by means of press-fit pins 34. The press-fit pins 34 are pressed into metal sleeves 36 that penetrate the circuit board 10. The waveguide structure is thus precisely positioned in the plane of the circuit board 10. A coupling dome 26 serves as a spacing retainer, which also precisely defines the spacing between the waveguide structure 12 and the circuit board 10.

[0030] In the example shown, the press-in pins 34 are arranged on the edge of the metal plate 32 and are integrally formed from the material of the metal plate. During manufacturing, the metal plate 32 is stamped from a metal blank such that the metal strips that subsequently form the press-in pins 34 originate from the edge of the main portion of the metal plate. These metal strips each have the desired shape of the press-in pins 34 at their ends, having a width and thickness that match the dimensions of the sleeve 36, and having eyelets 38 that allow for precise measurement of the press-in force. The metal strips are then bent by 90° each, so that the press-in pins extend at right angles to the plane of the metal plate 32.

[0031] The sleeve 36 can be connected to the grounding conductor of the conductor structure 14, thereby keeping the metal plate 32 at ground potential.

[0032] Although in the example shown, the press-in pins 34 are formed only on the two parallel edges of the metal sheet 32, a variant implementation is also conceivable in which the press-in pins are also arranged on the other two edges of the metal sheet. This allows for a more precise placement of the waveguide structure 12 relative to the circuit board 10 if necessary.

[0033] Another embodiment is conceivable in which the waveguide structure 12 is formed solely by single "islands" made of plastic, which form the sidewalls of channels 18, 20 and are sputtered onto the metal plate 32. In this case, the bottom of channels 18, 20 is formed by a conductive metal sheet 32.

[0034] Figure 2 A cross-sectional view of a high-frequency circuit is shown, which has the same characteristics as in... Figure 1 The same principle structure applies. However, here, an annular metallized surface 40 is formed on the surface of the circuit board 10 at the location of each coupling dome 26, which is congruent to the planar view (Grundriss) of the coupling dome 26 and surrounds the transmitter 30 with a gap. In this way, the air gap between the circuit board 10 and the coupling dome 26 forming the coupling channel 28 is electrically closed. Before the metallized surface 40 is installed, the conductor structure 14 connected to the transmitter 30 is covered by an insulating layer. In another embodiment, the metallized surface 40 is interrupted at the location of the conductor structure 14.

[0035] Figure 3 Showing has with Figure 1 and Figure 2The same high-frequency circuit with the same principle structure as the housing 42 that houses the high-frequency circuit is described. In this embodiment, a special feature is that springs 44 are arranged on the lower side of the circuit board 10 at the location of the coupling dome 26. The springs are supported at the bottom of the housing 42, and the circuit board 10 (which has a certain inherent elasticity) is partially pressed against the lower end surface of the coupling dome 26 to pre-tighten the springs, thereby ensuring the fixed placement of the circuit board on the coupling dome.

[0036] Figure 4 A cross-sectional view of a high-frequency circuit is shown in the following section: This section is relative to... Figures 1 to 3 The cross-section extends at right angles, thus allowing the press-in pins 34 to be seen from the side. However, in this example, the press-in pins 34 are arranged not only on the edges of the metal plates but also in the in-plane surfaces of the metal plates on both sides of the coupling dome 26. To manufacture these internal press-in pins 34, slots 46 (see...) are... Figure 5 These grooves, which are pressed into the metal sheet 32, define the profile shape of the press-in pin.

[0037] In this embodiment, the metal sheet also serves to dissipate heat generated in the component 16. For this purpose, the intermediate space between the component 16 and the metal sheet 32 ​​is filled with a thermally conductive material 48. Thus, the heat generated by the component 16 can be conducted to the circuit board 10 through the metal sheet 32 ​​and the press-fit pin 34, and then radiated through a larger surface area.

[0038] Figure 5 A variation of the implementation is shown in which a metal sheet 32 ​​forming a press-in pin 34 is arranged on the upper side of the waveguide structure 12. In this case, the waveguide structure 12 forms slits 50 through which the internal press-in pin 34 passes.

[0039] In this example, a metallization layer 52, for example made of copper, is applied to the surface of the circuit board 10 on the surface containing the complete plan view of the component 16. This metallization layer, together with the metallization of the waveguide structure 12 and the metal sheet 32, forms an EMV shield for the high-frequency module and also contributes to the heat dissipation of the MMIC.

[0040] exist Figure 6 The top view shows the data according to... Figure 5 The high-frequency circuitry is shown. The outlines of the circuit board 10 and the metal sheet 32 ​​can be seen, as well as the protrusions of the press-in pins 34 arranged at the edge of the metal sheet, the grooves 46 inside the metal sheet, and the protrusions of the press-in pins 34 there, which pass through the slits 50 of the waveguide structure. Furthermore, radiation openings 24 can be seen, in this case, formed in the metal sheet 32 ​​on the upper side of the waveguide structure.

[0041] According to Figure 5 and Figure 6 In one embodiment, component 16 is covered by waveguide structure 12, such that the waveguide structure (except for coupling dome 26) is positioned at a certain distance above circuit board 10. However, another embodiment is conceivable in which the waveguide structure is placed directly on circuit board 10 outside the plan view of component 16. In this case, metallization layer 52 may also extend on the base surface of waveguide structure 12 and form the bottom of waveguide channel.

[0042] Figures 7 to 9 The following embodiments are shown: In these embodiments, the transmitter 30 is integrated into the electronic component 16', thus eliminating the need for microstrip lines on the circuit board 10. Instead of a coupling dome, the waveguide structure 12 has a simple spacing maintainer 26', which ensures a defined spacing with the circuit board 10. Microwave power is coupled directly from the transmitter to the cavity in the waveguide structure 12 through a slit in the metal plate 32.

[0043] exist Figure 7 In this configuration, component 16' is arranged on the upper side of circuit board 10. Figure 8 In this configuration, component 16' is arranged on the underside of circuit board 10 and connected via ball grid array 54. In this configuration, microwave power coupling input occurs through a slit in circuit board 10.

[0044] exist Figure 9 The top view shows the data according to... Figure 8 The component 16'. The MMIC 56 is embedded in the plastic housing 58 and is in thermal contact with the housing through the heat transfer material 60. The emitter 30 is formed on or in the outer surface of the housing 58 (an emitter on the package or an emitter in the package) and is connected to the MMIC 56 via a high-frequency line not shown.

Claims

1. A high-frequency circuit having a circuit board (10) carrying at least one electronic component (16, 16') and a conductor structure (14), and having a waveguide structure (12) manufactured separately from the circuit board, the waveguide structure being positioned on the circuit board (10) such that a high-frequency signal can be transmitted between the conductor structure (14) and the waveguide structure (12) on the circuit board, characterized in that, The waveguide structure (12) is held on the circuit board (10) by means of a press-fit pin (34). The press-in pin (34) is integrally constructed with the metal plate (32) supporting the waveguide structure (12). The metal plate (32) and the press-in pin (34) are formed of metal sheets, wherein the press-in pin (34) is formed of a bent strip of the metal sheet.

2. The high-frequency circuit according to claim 1, wherein at least a plurality of the press-in pins (34) are located in the grooves (46) of the metal plate (32), wherein, In order to manufacture the at least several press-in pins (34), the grooves (46) are stamped into the metal plate (32), the grooves defining the outline shape of the at least several press-in pins (34).

3. The high-frequency circuit according to any one of claims 1 to 2, wherein the channels (18, 20) of the waveguide structure (12) are respectively limited by metallized walls of a plastic body on at least two opposite sides, and the metal plate (32) limits the channels on one of the remaining sides.

4. The high-frequency circuit according to claim 3, wherein one or more plastic bodies defining the channels (18, 20) of the waveguide structure (12) are arranged such that they are sandwiched between the metal plate (32) and another metal sheet (22).

5. The high-frequency circuit according to claim 4, wherein the waveguide structure (12) is a waveguide antenna, and the waveguide antenna has a radiating opening (24) in the metal plate (32) and / or the other metal sheet (22).

6. The high-frequency circuit according to any one of claims 1 to 2, wherein the metal plate (32) is part of the electromagnetic shielding of the component (16).

7. The high-frequency circuit according to any one of claims 1 to 2, wherein the metal plate (32) and the component (16) are in thermal contact through a heat conduction device (48).

8. The high-frequency circuit according to any one of claims 1 to 2, wherein the metal plate (32) is located on the side of the waveguide structure (12) opposite to the circuit board (10).

9. The high-frequency circuit according to claim 8, wherein a metallization layer (52) is applied to the surface of the circuit board (10), the metallization layer extending over the entire plan view of the component (16), and / or defining the waveguide structure (12) for the conduction of the waveguide channel on one side.

10. The high-frequency circuit according to any one of claims 1 to 2, wherein the waveguide structure (12) forms at least one coupling dome (26), in which a coupling channel (28) extends perpendicularly to the plane of the circuit board (10), wherein, The conductor structure (14) on the circuit board (10) forms a transmitter (30) for each coupling channel (28), the transmitter being disposed within the plan view of the coupling channel.

11. The high-frequency circuit according to claim 10, wherein each transmitter (30) is surrounded by an annular conductive surface (40) formed on the surface of the circuit board (10) and abutting against the end face of the coupling dome (26).

12. The high-frequency circuit according to claim 11, wherein the conductive surface (40) is formed by a conductive adhesive.

13. The high-frequency circuit according to claim 10, wherein the circuit board (10) is pre-tightened at the position of each coupling dome (26) by a spring (44) partially abutting against the coupling dome (26).

14. The high-frequency circuit according to any one of claims 1 to 2, wherein a transmitter (30) for coupling the high-frequency signal into the waveguide structure (12) is integrated into the electronic component (16').

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