Method for arranging a printed circuit board on a heat sink
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- HELLA GMBH & CO KGAA
- Filing Date
- 2019-03-19
- Publication Date
- 2026-07-09
AI Technical Summary
Existing methods for aligning a printed circuit board with a light source on a heat sink are complex and inflexible, requiring multiple components and machining steps to maintain precise tolerances between the light source and optically effective components like reflectors.
A method involving an optically detectable reference means on the heat sink, a manipulator for X-Y plane movement, and a camera for precise positioning, followed by bonding strips that also serve as heat conductors to secure the circuit board, ensuring accurate alignment and heat dissipation.
Achieves precise alignment of the light source relative to the optically effective component while providing efficient heat dissipation through bonding strips connected directly to the heat sink, maintaining +/-50 μm accuracy and enhancing cooling efficiency.
Smart Images
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Abstract
Description
[0001] The invention relates to a method for arranging a printed circuit board (PCB) with a light source mounted on the PCB on a heat sink. In subsequent use, the light source serves to shine light into an optically active component, for example, a transmissive optic or a reflector. The optically active component is positioned relative to the PCB and thus also relative to the light source, and tight tolerances must be maintained between the light source and the optically active component. Furthermore, a heat sink is often used, on which the PCB with the light source must be mounted to effectively dissipate heat from the light source on the PCB. STATE OF THE ART
[0002] EP 2 888 519 B1 discloses a method for arranging a printed circuit board with a light source on a heat sink, and a reflector is positioned on the circuit board such that tight tolerances can be maintained with respect to the relative position between the light source and the reflector. For this purpose, reference positions are to be created on the circuit board, to which the reflector is subsequently attached. The reference positions are positioned so that they maintain tight tolerances relative to the position of the light source on the circuit board. To ensure these tolerances, the position of the light source on the circuit board is measured with a camera, and the reference positions are created, for example, by machining at least two edges of the circuit board. The machining is carried out until the target position of the light source relative to the, for example, two reference positions is reached.When the reflector is later attached to the machined contact surfaces on the circuit board, a precise position between the position of the light source and the position of the reflector is made possible.
[0003] In the proposed method, the light source is placed in a predetermined position on the circuit board, and the circuit board with the reference positions is adapted to the actual measured position of the light source on the circuit board, for example, by milling stop edges or drilling holes. The proposed alternative, which involves fixing the light source to the circuit board and the circuit board to the mounting body, such as a heat sink, and then creating the reference for the reflector, is complex and requires machining.
[0004] EP 3 088 798 B1 describes a method for arranging a printed circuit board with a light source relative to an optically effective component. The method determines the positional difference between the actual position and a required target position of the light source relative to the optically effective component. Finally, the printed circuit board with the light source is moved relative to the optically effective component until the actual position of the light source matches the required target position. In this system, the optically effective component, such as a reflector, is also included in the adjustment of the light source, making the method less flexible and more complex, as several components are involved in the alignment.
[0005] A more desirable method involves providing a unit consisting of a circuit board, a light source, and a mounting body, particularly a heat sink, and aligning this unit against a reference. This reference then allows the optically active component, such as a reflector with a reflector base, to be positioned against the reference. The reference should be designed so that the light source ultimately occupies the required target position relative to the optically active component. REVELATION OF THE INVENTION
[0006] This problem is solved starting from a method according to claim 1 with the characterizing features. Advantageous embodiments of the invention are specified in the dependent claims.
[0007] The method according to the invention proposes the following process steps: providing the heat sink with an optically detectable reference means; providing a manipulator for moving the printed circuit board in an XY plane on a receiving surface of the heat sink; providing a camera for detecting the XY position of the reference means and the XY position of the light source; determining a deviation of the XY position of the light source relative to a target position of the light source in the XY plane relative to the XY position of the reference means by means of the camera; moving the printed circuit board with the manipulator in the XY plane until the light source is arranged in the target position and creating a bond connection with several bond ribbons between the printed circuit board and the heat sink.
[0008] The core concept of the invention is the detection of a reference position on a heat sink, which can also generally serve as a mounting plate or the like, thus also forming a heat sink. This heat sink has arbitrarily diverse reference elements on its mounting surface, such as elongated holes, bores, projections, or the like, which can be detected by the camera. Simultaneously, the position of the light source in the XY plane is detected, and the difference between the actual position and the target position of the light source relative to the reference elements can be determined. Finally, the circuit board with the light source is moved via a control unit using a manipulator until the light source reaches the target position in the XY plane.Subsequently, according to another key concept of the invention, the circuit board is fixed to the heat sink by creating a bond connection, and the bond connection comprises several bond ribbons.
[0009] The bonding strips are designed to primarily serve a cooling function for the light source by directly connecting them to the heat sink. For example, the bonding strips can be flat ribbons or wires (bond wires), and heat generated in the light source during operation is dissipated directly to the heat sink via the multiple bonding strips. Heat conduction through the circuit board to the heat sink is then only partially or not at all possible. The bonding connection can optionally also serve for electrical contact with the circuit board, particularly if the heat sink's receiving surface has appropriately insulated contacts to which the bonding strips are attached and electrically connected.
[0010] An advantageous embodiment of the method provides that the reference means are formed by means of receiving openings in the heat sink, through which an optically active component is positioned above the circuit board and the light source in a subsequent step. If, according to the invention, the position of the light source is aligned with the positions of the reference means in the XY plane, the optically active component, for example a reflector, can advantageously be arranged on the reference means. The result is a precise alignment of the optically active component with the emitter surface of the light source.
[0011] It is also advantageous that the circuit board is only released by the manipulator after the bond connection has been created using multiple bond strips. The manipulator can be a gripper that grasps the circuit board in such a way that it can move the board planarly in the XY plane and hold it in the desired position until the bond strips have been formed.
[0012] The bonding strips are advantageously formed with a copper alloy, a copper-based material, or, as a particular advantage, on an aluminum alloy. If the bonding strips are directly connected to the heat sink material, this results in an advantageous material pairing for welding the bonding strips to the heat sink material in the bonding process (wire bonding).
[0013] A further advantage is achieved when the bonding strips are of such a length that, after the bond is established, a tensile stress builds up in the bonding strips, which presses the circuit board onto the receiving surface of the heat sink. This results in additional heat conduction from the circuit board to the heat sink, particularly for further cooling of the light source via the bonding strips.
[0014] The camera for capturing the XY position of both the reference medium and the light source can be connected to an image processing unit. The determination of any deviation of the XY position of the light source from the target position relative to the reference medium is performed by the image processing unit using image analysis, in particular based on an image or video captured by the camera and transmitted to the image processing unit. The positioning accuracy of the light source relative to the reference medium(s) can be determined to, for example, approximately + / - 50 µm.
[0015] A further advantage is that the camera is positioned above the heat sink's receiving surface, allowing the camera to capture both the position of the light source and the reference element in a single image or video. The camera is positioned in a bird's-eye view above the heat sink and thus also above the circuit board containing the light source. The reference element is located adjacent to the circuit board and light source within the heat sink's receiving surface, for example, in the form of holes, slots, protrusions, or similar features. The camera can then capture both the reference element and the optical center of the light source, which can be determined geometrically or by the light source's operation, allowing the camera to capture a maximum light intensity.
[0016] According to a further aspect of the invention, a Z-position can also be achieved with the circuit board and ultimately for the light source. For example, it is possible to temporarily or permanently lift the circuit board from the receiving surface of the heat sink into a Z-position using a lifting device in order to position the light source into the Z-position. The lifting device can be used either during or after the formation of the bond connection with the multiple bond strips between the circuit board and the heat sink.
[0017] If the lifting device is used after the bond connection has been made, the bond strips must be of a length that prevents tension and allows for a certain degree of spring compliance to position the circuit board at the target Z-position above the heat sink's receiving surface. The bond connections can act as spring elements in this process. If the lifting device is not removed after lifting the circuit board, it can remain integrated with the circuit board and heat sink, serving as a Z-positioning element even during operation of the assembled lighting unit. In particular, if the bond strips are manufactured only after the circuit board has been specified, the raised target Z-position of the circuit board can be maintained via the bond connection during subsequent operation of the unit.
[0018] As an alternative to a lifting device, the method involves first positioning the printed circuit board (PCB) above the heat sink at a distance from the receiving surface. Only after the bond connection with the multiple bonding strips has been established above the light source is the optically active component positioned. This component then presses the PCB downwards towards the receiving surface of the heat sink by a path geometrically defined by the optics, thus precisely determining the Z-position of the PCB. For this purpose, the optically active component, for example, a transmittive optic made from an injection-molded part, can have associated pressure pins that press the PCB downwards. Finally, the optics are connected to the heat sink via the reference means. PREFERRED EXAMPLE OF THE INVENTION
[0019] Further measures improving the invention are described in more detail below, together with a description of a preferred embodiment of the invention, with reference to the figures. The figures show: Fig. 1. A top view of the arrangement of a printed circuit board on a heat sink, Fig. 2 a side view of the circuit board on a heat sink with a camera and with a manipulator, Fig. 3 a side view of the circuit board with the light source arranged on a heat sink, Fig. 4 a top view of the arrangement according to Fig. 3, Fig. 5a-5c the application of a lifting device for raising the printed circuit board above the receiving surface of the heat sink and Fig. 6a, Fig. 6b the arrangement of an optically effective component above the light source on the circuit board, while the optically effective component sets a Z-position of the circuit board above the heat sink.
[0020] Fig. Figure 1 shows a heat sink in a top view. 12 with a top-side recording surface 12a , and on the heat sink 12 are reference means 13 in the form of intake openings 18 inserted. Between the two depicted receiving openings. 18 is a printed circuit board 10 with one on the circuit board 10 arranged light sources 11 arranged. In schematic representation, it is located above the circuit board. 10 a manipulator 14 The circuit board 10 even has a quiver 24 on, via which the manipulator 14 the circuit board in a manner not shown in detail 10grasp and in the flat plane of the recording surface 12a can be shifted in the X and Y directions.
[0021] The circuit board 10 is on the heat sink 12 by means of a bond connection 16 attached, and the bond connection 16 shows, for example, four Bond ribbons 17 up. The Bond ribbons 17 are directly connected to the recording surface 12a of the heat sink 12 connected, and can - only optionally - also include an electrical contact of the light source. 11 The basic idea of the invention, however, is the mounting and heat dissipation of the light source. 11 about the Bond ribbons 17 , which are directly related to the material of the heat sink 12 connected, especially welded.
[0022] Fig. Figure 2 shows the arrangement of the circuit board 10 on the heat sink 12 according to Fig. 1 in a side view, with the manipulator also 14 with assigned grippers 23 and a camera 15 are shown in more detail. The circuit board 10 is with light bulb 11 on the recording surface 12a of the heat sink 12 applied, and the camera can determine the position of the light source. 11 Capture according to a process step. The printed circuit board 10 The gripper is used in this process. 23 gripped and can be placed in the plane above the recording surface 12a The camera is shifted in the X and Y directions. At the same time, it captures... 15 the reference means 13 (see Fig. 1), and the camera 15 is equipped with an image evaluation unit 20 connected to which the positions of the light source 11 and the reference means 13 The results from the image analysis unit can be compared using additional means not shown.20 , namely the deviation between a target position and an actual position of the light source 11 relative to the reference means 13 a message to the manipulator 14 be transmitted so that a correction path is created, via which the light source 11 is brought into the target position in order to assume the target position relative to the reference means in the XY plane.
[0023] The bond connection is then 16 with the Bond ribbons 17 produced, which is depicted in Fig. 1. Through the bond connection 16 This results in an unchanging position of the circuit board. 10 and thus also the light source 11 on the recording surface 12a of the heat sink 12 , and that also defines the target position of the light source. 11 relative to the reference means 13 in the form of the intake openings 18 guaranteed.
[0024] The Fig. 3 and Fig. 4. The circuit board is shown again in a side view and in a top view. 10 arranged on the recording surface 12a of the heat sink 12 This example illustrates an alternative design of the bond connection. 16 with the Bond ribbons 17 , which are on bond surfaces 25 on the circuit board 10 are attached, and have an opposite end on the recording surface 12a of the heat sink 12 are connected.
[0025] The manipulator 14 It is simplified and represented with a crosshair and a curved arrow, which illustrates that the manipulator 14 the circuit board 10 can be moved both in the XY plane and in a rotation, and the manipulator 14 can be used with the circuit board 10 via assigned trap holes 24can be connected. This allows the circuit board to be connected. 10 It can be adjusted both translationally and rotationally. The result after adjustment by the manipulator is... 14 an exact position of the light source 11 relative to the reference means 13 .
[0026] The Fig. 5a, Fig. 5b and Fig. 5c shows an embodiment according to which a lifting device 21 the circuit board 10 with the light source 11 above the recording surface 12a of the heat sink 12 It can be lifted. For this purpose, the lifting device is used. 21 , exemplified as a lifting piston, from below through an opening through the cooling body 12 through to the underside of the circuit board 10 driven to finally remove the circuit board 10 to lift. The circuit board is involved. 10 already with the Bond ribbons 17 with the heat sink12 tied together.
[0027] Fig. 5a shows the arrangement of the lifting device 21 except for interfering with the circuit board 10 .
[0028] Fig. 5b shows the lifting device 21 during the lifting of the circuit board 10 , by the lifting device 21 against the underside of the circuit board 10 is being driven. Will be according to Fig. 5c the lifting device 21 Once removed, the circuit board remains. 10 in the position above the recording surface 12a of the heat sink 12 This allows for a Z-position of the light source. 11 above the heat sink 12 The lifting device must be adjusted. 21 Alternatively, it can also be arranged according to Fig. 5b remain to assemble the circuit board 10 in the Z-position above the recording surface 12a of the heat sink 12 to maintain permanently.
[0029] The Fig. 6a and Fig. Figure 6b shows the arrangement of an optically effective component in successive steps. 19 on the heat sink 12 To the optically effective component 19 above the light source 11 on the circuit board 10 To position them precisely, they are located on the optically effective component. 19 Positioning pin 26 attached, which fit into the receiving openings 18 can be fitted precisely. The circuit board 10 is at a distance above the recording surface 12a of the heat sink 12 arranged and over the bond ribbons 17 held.
[0030] The optically effective component 19 shows printing stamp 22 up, and in the direction of the arrow shown, the optically effective component 19 contrary to the circuit board 10 moved downwards while the positioning pins 26into the intake openings 18 to intervene, the pressure stamps press down 22 the circuit board 10 by a smaller amount towards the recording surface 12a , which allows for precise positioning of the light source 11 to the optically active part 19a of the optically effective component 19 results.
[0031] The invention is not limited in its implementation to the preferred embodiment described above. Rather, a number of variants are conceivable, which utilize the solution presented even in fundamentally different designs. All features and / or advantages arising from the claims, the description, or the drawings, including design details, spatial arrangements, and process steps, can be essential to the invention, both individually and in various combinations. Reference symbol list 10 circuit boards 11 light bulbs 12 heat sinks 12a Recording surface 13 reference means 14 Manipulator 15 cameras 16 Bond connection 17 Bond ribbons 18 Inlet opening 19 optically effective component 19a optically active area 20 image evaluation units 21 Lifting device 22 printing stamps 23 grippers 24 Catching Hole 25 Bond area 26 positioning pins QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] EP 2888519 B1
[0002] EP 3088798 B1
[0004]
Claims
[1] Method for arranging a printed circuit board (10) with a light source (11) applied to the printed circuit board on a heat sink (12), wherein the method comprises at least the following steps: - Providing the heat sink (12) with an optically detectable reference medium (13), - Providing a manipulator (14) for moving the printed circuit board (10) in an XY plane on a receiving surface (12a) of the heat sink (12), - Providing a camera (15) to capture the XY position of the reference medium (13) and the XY position of the light source (11), - Determination of a deviation of the XY position of the light source (11) relative to a target position of the light source (11) in the XY plane relative to the XY position of the reference source (13) using the camera (15), - Moving the circuit board (10) with the manipulator (14) in the XY plane until the light source (11) is in the desired position and - Establishing a bond connection (16) with several bond ribbons (17) between the circuit board (10) and the heat sink (12). [2] Method according to claim 1, characterized by , that the bond ribbons (17) are directly connected to the receiving surface (12a) of the heat sink (12). [3] Method according to claim 1 or 2, characterized by , that the reference means (13) are formed by means of receiving openings (18) in the heat sink (12), through which an optically effective component (19) is positioned over the circuit board (10) and the light source (11) in a subsequent step. [4] Method according to any one of claims 1 to 3, characterized by , that the circuit board (10) is only released by the manipulator (14) after the bond connection (16) has been made with several bond ribbons (17). [5] Method according to any of the aforementioned claims, characterized by , that a copper material, a copper-based material or an aluminum material is used to form the bond ribbons (17). [6] Method according to any of the aforementioned claims, characterized by , that the bond ribbons (17) are determined in their length such that after the bond connection (16) is made a tensile stress is built up in the bond ribbons (17) by means of which the circuit board (10) is pressed onto the receiving surface (12a) of the heat sink (12). [7] Method according to any of the aforementioned claims, characterized by, that the camera (15) is connected to an image evaluation unit (20), wherein the determination of a deviation of the XY position of the light source (11) relative to a target position of the light source (11) in the XY plane relative to the reference source (13) is carried out by means of an image evaluation by the image evaluation unit (20) of an image or video recorded with the camera (15). [8] Method according to any of the aforementioned claims, characterized by , that the camera (15) is positioned above the recording surface (12a) of the heat sink (12) so that the position of the light source (11) and the position of the reference means (13) are captured in an image or in a video using the camera (15). [9] Method according to any of the aforementioned claims, characterized by, that the circuit board (10) is lifted from the receiving surface (12a) of the heat sink (12) into a Z target position by means of a lifting device (21) in order to position the light source (11) into the Z target position. [10] Method according to claim 9, characterized by , that the lifting device (21) is used during or after the production of the bond connection (16) with the multiple bond ribbons (17) between the circuit board (10) and the heat sink (12). [11] Method according to claim 9 or 10, characterized by , that the circuit board (10) is fixed in the set Z-position with or after the removal of the lifting device (21). [12] Method according to any one of claims 1 to 8, characterized by, that the printed circuit board (10) is arranged at a distance from the receiving surface (12a), wherein, after the bond connection (16) has been made with the several bond ribbons (17) above the light source (11), the optically effective component (19) is arranged, with which the printed circuit board (10) is pressed downwards by a geometrically defined path in the direction of the receiving surface (12a) of the heat sink (12), thereby determining the Z-position of the printed circuit board (10).