Circuit board with optically reflective measuring surface

Abstract

The invention relates to a circuit board (1) comprising a plurality of electrical and / or electronic components, wherein at least three optically reflective measuring surfaces (2) are formed on a surface (1A) of the circuit board (1), the measuring surfaces having a predetermined mutual distance and defining the plane of the circuit board (1).

Description

Technical Field

[0001] The invention relates to a circuit board comprising a plurality of electrical and / or electronic components.

[0002] In the case of such circuit boards known per se, it is necessary in certain cases to know the exact position of the circuit board and to perform corrections if necessary.

[0003] The present invention is particularly well suited for radar sensors in which the printed circuit board has at least one radar antenna structure arranged on a surface of the printed circuit board and a housing which surrounds the printed circuit board.

[0004] The invention further relates to a method for determining the relative position of a printed circuit board in a housing or in a support frame. Background Art

[0005] Such circuit boards, and in particular radar sensors, are known per se and are used, for example, in motor vehicles for driver assistance systems, such as distance measurement to vehicles ahead. The installation position of the radar sensor, and therefore the radar antenna structure, on the associated motor vehicle must be determined very precisely in order to define the radar antenna's transmission and reception directions and thus ensure sufficiently accurate distance, angle, and speed measurements. The installation position of the circuit board is determined, on the one hand, by securing the housing to which the circuit board is attached to the motor vehicle, and, on the other hand, by the position of the circuit board within the housing.

[0006] In addition to the antenna structure, a number of electrical and / or electronic components are arranged on the circuit board. Many of these components protrude from the surface of the circuit board on which the antenna structure is located. These components can reflect radar beams (so-called parasitic reflection effects) and potentially lead to erroneous measurements. During the design of the circuit board, these reflections are simulated, and the component arrangement is gradually optimized with respect to reflections. This optimization is checked using measurements on prototypes and, if necessary, continued.

[0007] Typically, the radar sensor, including the printed circuit board, is arranged in a housing to protect it from mechanical forces, dirt, and moisture. The portion of the housing that is located in front of the printed circuit board in the antenna's transmission or reception direction must be transparent to the radar beam and is therefore designed as a radome, for example, in the form of a housing cover (lid).

[0008] The radome also affects the radar beam, particularly the emitted radar beam. This influence depends primarily on the clear distance between the antenna (i.e., the circuit board) and the inner surface of the radome. This is due to the fact that local reflection varies with distance and has an optimal distance.

[0009] According to the prior art, the radome is fixed to the rest of the housing using, for example, adhesive or screws. This precludes the ability to adjust the distance between the antenna and the radome. During a final inspection, the radar sensor is checked in a so-called calibration room to see if it meets the requirements within predefined tolerances. This eliminates the need for calibration, reducing the relatively high scrap rate. Summary of the Invention

[0010] A first object of the present invention is to provide a circuit board whose relative position can be precisely determined and, if necessary, corrected.

[0011] The first object is achieved by forming at least three optically reflective measuring surfaces on the surface of the printed circuit board. These measuring surfaces have a predetermined mutual distance and define the plane of the printed circuit board. Antenna structures, for example, are arranged in this plane. This creates a precisely defined reference surface on the surface of the printed circuit board that can be detected using measurement technology. This allows the relative position of the printed circuit board, for example, relative to the radome, the support frame, or the housing floor, to be precisely determined and used for any necessary corrections.

[0012] In one embodiment, the measuring surfaces are arranged in opposite edge regions of the surface. This allows for the most accurate determination of the position of the printed circuit board. Furthermore, the measurement is less susceptible to interference from components. The structure of the printed circuit board with its conductor tracks and components can be planned and implemented largely independently of the measuring surfaces, as the edge regions are generally less utilized.

[0013] In another embodiment, the measuring surface is made of copper. This simplifies the production of the printed circuit board, since the printed circuit board already contains copper, for example, for the conductor tracks. Furthermore, a surface made of copper has good optical reflection properties.

[0014] The measuring surface can have a coating, for example lacquer or chemical tin.

[0015] In another embodiment, the four measuring surfaces are arranged in a mirror-symmetrical manner, thereby enabling particularly accurate measurements with low computer power.

[0016] In another embodiment, the printed circuit board is assigned to a radar sensor and has at least one radar antenna structure arranged on the surface for transmitting and receiving radar radiation. For radar sensors, a mounting position that is as accurate as possible is particularly important.

[0017] In another embodiment, the printed circuit board is surrounded by a housing, wherein at least one portion of the housing is transparent to the laser beam.

[0018] The radar sensor's radome—that is, the radar antenna's cover that is transparent to the radar beam—is designed to be transparent to the laser beam. The radome must maintain a very precise, predetermined distance from the radar antenna structure to minimize undesirable local reflections of the radar beam from the radome. This distance can be determined using the laser beam due to its transparency, with the measuring surface serving to reflect the laser beam.

[0019] Furthermore, the radome can be attached to the base or support frame by laser welding. This allows the distance between the radar antenna structure and the inner side of the radome to be adjusted, for example, by adjusting the intensity and / or duration of the laser beam accordingly. This causes a correspondingly larger or smaller amount of radome material to melt at the abutment edge with the base or support frame, allowing the optimal distance to be set. This allows manufacturing tolerances of the radome and base or support frame to be compensated during final assembly, resulting in a very good overall function of the radar sensor.

[0020] A second object is to provide a method with which the relative position of the printed circuit boards can be determined very accurately and, if necessary, corrected.

[0021] The second object is achieved by measuring the distance between a respective one of at least three optically reflective measuring surfaces and the measuring instrument by means of at least one optical measuring instrument, and comparing the distance with a reference distance, wherein the measuring surface is arranged on a surface of the printed circuit board and the surface is directed toward the measuring instrument during the measurement.

[0022] The measuring surface provides a well-defined reference surface for distance measurement and thus for relative position and thus for the relative position of the plane of the circuit board, wherein the position is corrected if necessary. In this way, the target position of the circuit board can be achieved very accurately.

[0023] The method can be used particularly advantageously for assembling radar sensors. This applies correspondingly to the corresponding device claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will now be explained in detail with the aid of the accompanying drawings.

[0025] Figure 1 shows a top view of a printed circuit board (without components and conductor tracks),

[0026] Figure 2 A side view showing a measuring instrument with a printed circuit board, partially broken away, and

[0027] Figure 3 A longitudinal section through a radar sensor and a measuring instrument and a welding device arranged above it is shown. DETAILED DESCRIPTION

[0028] As Figure 1 As can be seen, four measuring surfaces 2 are arranged on the rectangular surface 1A of the circuit board 1. These measuring surfaces define the plane of the surface 1A and, therefore, the plane of the circuit board 1. Each pair of measuring surfaces 2 is arranged at a predetermined distance from one another on a long side of the surface 1A such that the measuring surface 2 on one of the long sides is perpendicular to the longitudinal axis of the circuit board 1 relative to the measuring surface on the other long side. Consequently, the line connecting the center points of the four measuring surfaces 2 forms a rectangle. The long-side spacing of the measuring surfaces 2 is as large as possible.

[0029] The measuring surface 2 is optically reflective and is formed, for example, from a thin copper layer. The measuring surface can be coated, for example, with lacquer or chemical tin.

[0030] A through-hole 3 is introduced in the region of each corner of the circuit board 1 in order to be able to mechanically position the circuit board 1 in the desired position. Figure 1 The housing or support frame (not shown) can be fixed thereto if necessary.

[0031] The printed circuit board 1 comprises a plurality of conductor tracks and electrical and / or electronic components (not shown). An antenna structure may be arranged on the surface 1A.

[0032] The printed circuit board 1 can be electrically connected to a control and evaluation device directly or preferably indirectly via a plug connector.

[0033] Depend on Figure 2 It can be seen how measuring surface 2 is used. Circuit board 1 is held in base 4A of housing 4, with surface 1A of the circuit board pointing toward the opening in base 4A. The offset of circuit board 1 in base 4A and the height (material thickness) of measuring surface 2 are clearly shown as exaggerated.

[0034] Two measuring devices 5 are fixed at a predetermined distance from the surface 1A (here above), wherein each measuring device 5 is assigned to at least one measuring surface of the measuring surface 2. The measuring devices 5 are designed for distance measurement using a laser beam.

[0035] To determine the relative position of the circuit board 1, the base 4A and the circuit board 1 are positioned below a measuring instrument 5. The actual distance of each measuring surface 2 from at least one of the measuring instruments 5 is determined by the measuring instrument and compared with a reference distance in an evaluation device.

[0036] When the deviation between the actual distance and the reference distance is not allowed to be large, the relative position of the circuit board 1 in the bottom 4 a is corrected accordingly.

[0037] exist Figure 3FIGURE 1 shows a preferred application of a circuit board in a radar sensor. A circuit board 1 is arranged in a housing 4, which consists of a base 4A and a lid-like cover 4B. The circuit board 1 is fixed to the base 4A so that the surface 1A with the antenna structure and the measuring surface 2 faces the open side of the base 4A. The measuring surface 2 defines the plane of the circuit board 1 and, therefore, the plane of the antenna structure. The cover 4B is designed as a radar radome and closes the open side of the base 4A (for the purpose of explaining the housing components, the cover 4B is shown in FIGURE 11 ). Figure 3 The cover 4B is also transparent to the laser beam.

[0038] The antenna structure includes at least one transmitting antenna and at least one receiving antenna.

[0039] In order to determine the relative position of the circuit board 1 , the measuring instrument 5 is arranged as described above.

[0040] In order to connect the base 4A to the cover 4B, a welding device 6 is provided which operates with a laser beam and is shown here between the measuring devices 5 .

[0041] The radar sensor is manufactured as follows:

[0042] The printed circuit board 1 is produced with the required conductor paths including the antenna structure and the measuring area 2 and is equipped with components.

[0043] The bottom portion 4A is formed by injection molding of plastic.

[0044] The cover 4B is made of a special plastic that contains a high-frequency absorbing material and is transparent to the laser beam.

[0045] The printed circuit board 1 is inserted into a predetermined position by means of the through-holes 3 and corresponding pins on the base 4A and is simultaneously fixed to the base 4A, for example, by clamping or latching, or subsequently, for example, by means of screws.

[0046] By inserting the printed circuit board 1 , an electrical connection to a socket formed on the housing 4 is achieved.

[0047] The bottom 4A is closed by a cover 4B to form a housing 4. The relative position of the circuit board 1 in the housing 4 (and therefore the clear distance between the surface 1A (plane) of the circuit board 1 and the inner side of the cover 4B) is determined very accurately by means of a measuring instrument 5 and a measuring surface 2 and compared with a reference distance.

[0048] The bottom 4A and the cover 4B are welded to each other at the butt joint, and the weld beam extends through the cover 4B.

[0049] If the measured distances and the reference distances lie within the tolerance limits at all locations, the welding is carried out uniformly over the entire circumference.

[0050] If the measured distance and the reference distance are not within tolerance limits at all locations, welding is performed by varying the welding intensity so that more shell material melts at the corresponding locations to reduce the distance and less shell material melts at other locations.

[0051] This allows for compensating for manufacturing tolerances in the individual components of the radar sensor, resulting in a radar sensor with very high measurement accuracy. Variations in the measurement accuracy of different radar sensors within a product series are minimized, ensuring overall good usability of the radar sensor thanks to the standardized software.

[0052] Reference Signs List

[0053] 1 circuit board

[0054] 1A surface

[0055] 2 measuring surface

[0056] 3 through holes

[0057] 4 shell

[0058] 4A bottom

[0059] 4B cover

[0060] 5. Measuring instruments

[0061] 6. Welding device

Claims

1. A method for determining and correcting the relative position of a circuit board (1) in a housing (4) or in a support frame, characterized in that: The distance between a corresponding one of at least three optically reflective measuring surfaces (2) and the measuring device (5) is measured by means of at least one optical measuring device (5), the distance is compared with a reference distance, and the comparison value is used to correct the relative position of the circuit board (1) in a housing (4) or in a support frame during final assembly, wherein the measuring surface (2) is arranged on a surface (1A) of the circuit board (1).

2. The method according to claim 1, characterized in that The method is used for final assembly of a radar sensor, a circuit board (1) is inserted into a housing (4), a cover (4B) of the housing is designed as a radar antenna cover that is transparent to laser beams, and the comparison value is used to correct the distance between the surface (1A) and the cover (4B).

3. Circuit board (1), comprising: a plurality of electrical and / or electronic components, Characterized in that at least three optically reflective measuring surfaces (2) are formed on the surface (1A) of the circuit board (1), which measuring surfaces have a predetermined mutual distance and define the plane of the circuit board (1), and the relative position of the circuit board (1) in the housing (4) or in the support frame is determined and corrected by the method according to claim 1 or 2.

4. The circuit board (1) according to claim 3, characterized in that: The measuring surfaces (2) are arranged in opposite edge regions of the surface (1A).

5. The circuit board (1) according to claim 3 or 4, characterized in that: The measuring surface (2) is made of copper.

6. The circuit board (1) according to claim 3 or 4, characterized in that: The four measuring surfaces (2) are arranged in a mirror-symmetrical manner.

7. The circuit board (1) according to claim 3 or 4, characterized in that: The printed circuit board is associated with the radar sensor and has at least one radar antenna structure arranged on the surface (1A).

8. The circuit board (1) according to claim 3 or 4, characterized in that: The circuit board is surrounded by a housing (4), wherein at least a portion of the housing (4) is transparent to the laser beam.

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