High frequency circuit with substrate and waveguide structure

Abstract

To enable precise positioning and secure fixing of a waveguide structure on a substrate at low manufacturing cost.SOLUTION: A high frequency circuit includes a substrate (10) that supports at least one electronic component (16) and a conductor structure (14), and a waveguide structure (12) manufactured separately from the substrate, and this waveguide structure (12) is positioned on the substrate (10) such that a high frequency signal can be transmitted between the conductor structure (14) and the waveguide structure (12) on the substrate. The waveguide structure (12) is held on the substrate (10) by a press-fit pin (34).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high frequency circuit comprising a substrate supporting at least one electronic component and a conductor structure, and a waveguide structure fabricated separately from the substrate, the waveguide structure positioned on the substrate to allow transmission of high frequency signals between the conductor structure on the substrate and the waveguide structure.

[0002] The present invention relates to high frequency circuits that are part of radar sensors, especially for automobiles. [Background technology]

[0003] In automobiles, radar sensors are used to capture the traffic environment in connection with driver assistance or safety systems, such as electronic distance control systems or collision warning systems. In order to obtain as complete an image of the traffic situation as possible, the radar sensor should have a wide capture range, especially in azimuth. For this purpose, radar sensors having high-frequency circuits of the type mentioned at the beginning and a waveguide structure serving as a waveguide antenna for transmitting and / or receiving radar signals are often used.

[0004] The conductor structure on the substrate forms a feeder, a so-called launcher, through which a high-frequency signal can be coupled to the waveguide structure, or conversely, a received radar signal is coupled to the conductor structure and transmitted to the electronics for signal evaluation. For a flawless signal transmission, it is important that the waveguide structure is positioned very precisely relative to the launcher.

[0005] In some conventional high-frequency circuits in the field of technology to which the present invention pertains, waveguide structures, for example, plastic moldings with metallized walls, are held on a substrate by screw connections, which has the disadvantage that the heads of the fastening screws occupy a relatively large area on the side of the substrate facing away from the waveguide structure, thus rendering this area unusable for electronic components and conductor paths.

[0006] One known alternative is to use adhesive bonding instead of screw bonding. This certainly reduces the space used on the board, but the manufacturing process is more cumbersome, especially since the adhesive must be cured at high temperatures. This requires a heated chamber in which the high-frequency circuits remain for a relatively long time, so high productivity can only be achieved with high equipment costs. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to enable precise positioning and reliable fixing of a waveguide structure on a substrate at low manufacturing costs. [Means for solving the problem]

[0008] This problem is solved according to the invention in that the waveguide structure is held on the substrate by press-fit pins.

[0009] The press-fit technique using press-fit pins has already been successfully used to establish an electrical connection between a printed circuit board and an electrical plug. When this technique is used to attach a waveguide structure on a substrate, the position of the waveguide structure relative to the launcher is predetermined by the position of a press-fit sleeve formed in the substrate, into which a press-fit pin located on the waveguide structure is then tightly and precisely pressed. Due to the force coupling of the press-fit pin within the sleeve, and possibly due to a diffusion process that establishes a metal-to-metal bond between the press-fit pin and the metal lining of the sleeve, a secure retention of the waveguide structure on the substrate is achieved without the need for time-consuming and expensive measures for curing adhesives.

[0010] Advantageous embodiments and variants of the invention are set out in the dependent claims. In one embodiment, the waveguide structure is formed by a plastic molding in which the transmission line is formed in accordance with the desired trajectory of the waveguide. The transmission line is not covered on the surface of the molding, which allows for smooth demolding during production of the molding. To form the waveguide structure, the walls of the transmission line are metallized, and the uncovered sides are closed with metal plates. In this case, press-fit pins can be easily manufactured by stamping out elongated strips of this metal plate and bending them at right angles, with the thickness of the metal plate and the width of the strip being selected to match the dimensions of the press-fit sleeve in the substrate.

[0011] This metal plate forming the press-fit pins can be on the side of the waveguide structure facing the substrate, or alternatively on the side facing away from the substrate, in the latter case the waveguide structure can be formed with through holes that can be penetrated by some of the press-fit pins, thereby achieving a substantially uniform distribution of the press-fit pins over the entire area of ​​the substrate.

[0012] Typically, the waveguide structure forms a coupling dome with a coupling transmission line, which extends perpendicular to the plane of the substrate and opens towards a launcher on the substrate. In one embodiment, a press-fit pin is pressed deep into a sleeve in the substrate so that the coupling dome abuts the substrate with a block. This minimizes dimensional errors.

[0013] The metal plate forming the press-fit pin can perform additional functions in addition to the mechanical fixing and positioning of the waveguide structure. For example, the metal plate can be part of an EMC shield for electronic components on the board. Furthermore, due to its excellent thermal conductivity, the metal plate can also be used to dissipate heat from the electronic components.

[0014] The launcher on the substrate can be surrounded by a conductive layer that completely closes the gap between the substrate and the end of the coupling dome electrically. Optionally, the conductive layer can be formed by a conductive adhesive that also contributes to mechanical fixation of the waveguide structure on the substrate.

[0015] In another embodiment, the substrate is elastically prestressed towards the edge of the coupling dome, particularly in the region of the coupling dome.

[0016] In the following, exemplary embodiments are explained in more detail on the basis of the drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a partially split-open perspective view of a radio frequency circuit according to one exemplary embodiment of the present invention; [Figure 2] 1 is a cross-sectional view of a high frequency circuit according to an exemplary embodiment of the present invention. [Figure 3] 10 is a cross-sectional view of a high frequency circuit according to a further exemplary embodiment of the present invention. [Figure 4] 10 is a cross-sectional view of a high frequency circuit according to a further exemplary embodiment of the present invention. [Figure 5] 10 is a cross-sectional view of a high frequency circuit according to a further exemplary embodiment of the present invention. [Figure 6] FIG. 6 is a plan view of the high-frequency circuit according to FIG. [Figure 7] 10 is a cross-sectional view of a high frequency circuit according to a further exemplary embodiment of the present invention. [Figure 8] 4 is a cross-sectional view of a high frequency circuit according to a further exemplary embodiment of the present invention; [Figure 9] FIG. 9 is a plan view of the high-frequency circuit according to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1 shows an example of a high-frequency circuit comprising a substrate 10 and a waveguide structure 12, which in this example is a waveguide antenna for a radar sensor. On its surface, the substrate 10 supports an electrical conductor structure 14, e.g., a microstrip line, and at least one electronic component 16, e.g., an MMIC (Monolithic Microwave Integrated Circuit), which generates a frequency-modulated radar signal that is subsequently radiated via the waveguide antenna and receives and further processes radar echoes from objects to be located.

[0019] The waveguide structure 12 is formed by a plastic block forming transmission lines 18, 20 with metallized side walls. The transmission lines are surrounded by a conductive surface on all sides and serve as waveguides for transmitting microwave signals. In the example shown in Figure 1, the depth of the transmission lines 18, 20 is less than the thickness of the plastic block, and the bottom of the transmission lines 18, 20 is formed by the metallized wall of the plastic block. The transmission lines 18, 20 are closed on the top by a metal plate 22, within which an emission port 24 for emitting the microwave beam is formed at a specific point of the waveguide.

[0020] The plastic block 12 of the waveguide structure forms coupling domes 26 at certain points, which protrude towards the substrate 10 and each define a vertical coupling transmission line 28, which is part of a waveguide network. On the substrate 10, in the cross section of the coupling transmission line 28 and precisely centered on the coupling transmission line, so-called launchers 30 are formed (see FIG. 2), which are connected to the component 16 via the conductor structure 14, and via which the microwave signal generated in the component 16 is coupled to the waveguide antenna.

[0021] 1, the plastic block that constitutes the waveguide structure 12 is fixedly placed on a lower metal plate 32, which is in turn fixed onto the substrate 10 by press-fit pins 34. Each of the press-fit pins 34 is press-fit into a metal sleeve 36 that passes through the substrate 10, thereby precisely positioning the waveguide structure within the plane of the substrate 10. The coupling domes 26 serve as spacers that also precisely define the distance between the waveguide structure 12 and the substrate 10.

[0022] In the example shown, the press-fit pins 34 are arranged on the edges of the metal plate 32 and are formed integrally from the material of this metal plate. During production, the metal plate 32 is stamped out from the blank sheet metal so that the metal strips that will become the press-fit pins 34 extend from the edges of the main part of the metal plate. At their ends, these metal strips each have the desired shape of the press-fit pins 34, in particular width and thickness that match the dimensions of the sleeve 36, as well as grooves 38 that allow for precise adjustment of the press-fit force. The metal strips are then each bent by 90°, so that the press-fit pins extend perpendicular to the plane of the metal plate 32.

[0023] The sleeve 36 can be connected to the ground conductor of the conductor structure 14, thereby keeping the metal plate 32 at ground potential.

[0024] While in the example shown the press-fit pins 34 are formed only on two parallel edges of the metal plate 32, a variant is also conceivable in which press-fit pins are also arranged on both other edges of the metal plate, thereby enabling a more accurate positioning of the waveguide structure 12 relative to the substrate 10 to be achieved if required.

[0025] Furthermore, an embodiment is contemplated in which the waveguide structure 12 is formed solely by a number of "islands" of plastic which form the side walls of the transmission lines 18, 20 and are injection molded to adhere to the metal plate 32. In this case, the bottom of the transmission lines 18, 20 is formed by the conductive metal plate 32.

[0026] 2 shows a cross section of a high-frequency circuit having the same basic structure as in FIG. 1. However, here, a ring-shaped metallization surface 40 is formed on the surface of the substrate 10 at the location of each coupling dome 26. This metallization surface 40 completely corresponds to the area occupied by the coupling dome 26 and surrounds the launcher 30 at a distance. This electrically closes the gap between the substrate 10 and the coupling domes 26 that form the coupling transmission path 28. The conductor structures 14 that contact the launchers 30 are covered with an insulating layer before applying the metallization surface 40. In another embodiment, the metallization surface 40 is interrupted at the locations of the conductor structures 14.

[0027] 3 shows a high-frequency circuit having the same basic structure as in Figures 1 and 2, together with a housing 42 in which the high-frequency circuit is accommodated. What is special about this exemplary embodiment is that springs 44 are arranged on the underside of the substrate 10, respectively at the location of the coupling domes 26, which are supported by the bottom of the housing 42 and locally prestress the substrate 10 (which has a certain degree of self-elasticity) towards the lower end faces of the coupling domes 26, thereby ensuring a fixed abutment of the substrate against the coupling domes.

[0028] 4 shows a cross section of the high-frequency circuit in a cut plane extending perpendicular to the cut planes in FIGS. 1 to 3, and therefore shows the press-fit pins 34 from the side. In this example, however, the press-fit pins 34 are not only located at the edges of the metal plate, but also inside the plane of the metal plate, on either side of the coupling dome 26. To produce these inner press-fit pins 34, slits 46 (see FIG. 5) are punched in the metal plate 32, which define the contours of the press-fit pins.

[0029] In this exemplary embodiment, the metal plate 32 is also used to evacuate heat generated within the component 16. To this end, the gap between the component 16 and the metal plate 32 is filled with a thermally conductive material 48. In this manner, the heat generated by the component 16 can be conducted into the substrate 10 via the metal plate 32 and the press-fit pins 34, and then radiated over a larger area.

[0030] 5 shows a variation in which the metal plate 32 forming the press-fit pin 34 is placed on top of the waveguide structure 12. In this case, the waveguide structure 12 forms a through hole 50 pierced by the inner press-fit pin 34.

[0031] In this example, a metal cladding layer 52, for example made of copper, is applied to the surface of the substrate 10, including the entire area occupied by the component 16, and together with the metal cladding of the waveguide structure 12 and the metal plate 32, this metal cladding layer 52 forms an EMC shield for the high-frequency module and at the same time contributes to heat dissipation of the MMIC.

[0032] Figure 6 shows a plan view of the high-frequency circuit according to Figure 5. The outlines of the substrate 10 and the metal plate 32 are visible, as are the bases of the press-fit pins 34 arranged on the edges of the metal plate, as well as the slits 46 inside the metal plate and the bases of the press-fit pins 34 therein, which pass through through-holes 50 in the waveguide structure. Furthermore, the radiation openings 24 formed in the metal plate 32 on the upper surface of the waveguide structure can be seen.

[0033] 5 and 6, the waveguide structure 12 is assembled on the component 16, so that the waveguide structure (except for the coupling dome 26) is spaced above the substrate 10. However, embodiments are also conceivable in which the waveguide structure rests directly on the substrate 10, outside the footprint of the component 16. In this case, the metallization layer 52 can also extend over the entire bottom surface of the waveguide structure 12 and constitute the bottom of the waveguide transmission line.

[0034] 7 to 9 illustrate an exemplary embodiment in which the launcher 30 is integrated into the electronic component 16′ and therefore no microstrip line is required on the substrate 10. Instead of a coupling dome, this waveguide structure 12 is provided with a simple spacer 26′ that ensures a defined spacing relative to the substrate 10. The coupling of the microwave power from the launcher into the hollow space of the waveguide structure 12 is performed directly via a through-hole in the metal plate 32.

[0035] In Figure 7, components 16' are located on the top surface of substrate 10. In Figure 8, components 16' are located on the bottom surface of substrate 10 and are contacted via ball grid array 54. In this case, microwave power coupling is via through holes in substrate 10.

[0036] 9 shows a plan view of the component 16' according to FIG. 8. The MMIC 56 is embedded in a plastic housing 58 and is in thermal contact with this housing via a heat transfer material 60. The launcher 30 is formed on or in the outer surface of the housing 58 (launcher on package or launcher in package) and is connected to the MMIC 56 via a high-frequency line (not shown). [Explanation of symbols]

[0037] 10 Substrate 12 Waveguide structure 14 Conductor structure 16;16' Electronic Components 18, 20 Transmission line 22 More Metal Plates 24 Radiation outlet 26 Coupling Dome 28 Coupling transmission line 30 Launcher 32 Metal plate 34 Press-fit pin 40 Conductive Surface 44 Spring 46 Slit 48 Heat Transfer Means 52 Metal coating layer

Claims

1. 1. A high-frequency circuit comprising: a substrate (10) supporting at least one electronic component (16; 16') and a conductor structure (14); and a waveguide structure (12) manufactured separately from the substrate, the waveguide structure (12) being positioned on the substrate (10) so that high-frequency signals can be transmitted between the conductor structure (14) on the substrate and the waveguide structure (12), the high-frequency circuit being characterized in that the waveguide structure (12) is held on the substrate (10) by press-fit pins (34).

2. 2. The high frequency circuit of claim 1, wherein the press-fit pin (34) is integrally formed with a metal plate (32) supporting the waveguide structure (12).

3. 3. The high frequency circuit of claim 2, wherein the metal plate (32) and the press-fit pin (34) are formed from a single piece of sheet metal, and wherein the press-fit pin (34) is comprised of a folded strip of the sheet metal.

4. 4. The high frequency circuit of claim 3, wherein at least some of the press-fit pins (34) are located within slits (46) in the metal plate (32).

5. 5. The high frequency circuit according to claim 2, wherein the transmission lines (18, 20) of the waveguide structure (12) are each defined by metallized walls of a plastic body on at least two mutually facing sides, and the metal plate (32) defines the transmission lines on one of the remaining sides.

6. 6. The high frequency circuit according to claim 5, wherein one or more plastic bodies defining the transmission paths (18, 20) of the waveguide structure (12) are arranged between the metal plate (32) and a further metal plate (22) in a sandwich manner.

7. 7. The high frequency circuit according to claim 6, wherein the waveguide structure (12) is a waveguide antenna with a radiation opening (24) in the metal plate (32) and / or the further metal plate (22).

8. 8. The high frequency circuit of claim 2, wherein the metal plate (32) is part of an electromagnetic shield for the component (16).

9. 9. The high frequency circuit of claim 2, wherein the metal plate (32) is in thermal contact with the component (16) via a heat conducting means (48).

10. 10. The high frequency circuit according to claim 2, wherein the metal plate (32) is on a side of the waveguide structure (12) opposite the substrate (10).

11. 11. The high frequency circuit according to claim 10, wherein a metallization layer (52) is applied to the surface of the substrate (10), the metallization layer (52) extending over the entire area occupied by the component (16) and / or defining the waveguide transmission path of the waveguide structure (12) on one surface.

12. 12. The high-frequency circuit according to claim 1, wherein the waveguide structure (12) forms at least one coupling dome (26) in which coupling transmission lines (28) extend perpendicular to the plane of the substrate (10), and wherein the conductor structure (14) on the substrate (10) forms for each coupling transmission line (28) a launcher (30) positioned within the footprint of the coupling transmission line.

13. 13. The high frequency circuit according to claim 12, wherein each launcher (30) is surrounded by a ring-shaped conductive surface (40), the conductive surface (40) being formed on the surface of the substrate (10) and abutting against an end face of the coupling dome (26).

14. 14. The high frequency circuit of claim 13, wherein the conductive surface (40) is formed by a conductive adhesive.

15. 13. The high frequency circuit of claim 12, wherein the substrate (10) is locally prestressed towards the coupling domes (26) by springs (44) at the location of each coupling dome (26).

16. 12. The high frequency circuit of claim 1, wherein the launcher (30) for coupling the high frequency signal to the waveguide structure (12) is integrated into the electronic component (16').

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