Method for assembling a plurality of light-emitting diodes on a printed circuit board to form a vehicle lighting module

Abstract

The invention relates to a method of assembling a plurality of light-emitting diodes (2) on a printed circuit board (4) in order to form a vehicle light module (6), the light module (6) comprising, in addition to the plurality of light-emitting diodes (2) and the printed circuit board (4), a grid (8) made of flexible material, said grid (8) being perforated in a plurality of openings (10) defining patterns, the set of patterns (10) being intended to define individual light patterns in the form of light pixels.According to the invention, the method comprises a step (20) of pre-positioning the light-emitting diodes (2) with respect to the patterns of the grid (8); a step (22) of positioning the matrix (12) of light-emitting diodes (2) on the printed circuit board (4), each light-emitting diode (2) of the matrix (12) of light-emitting diodes (2) being positioned on the printed circuit board (4) at a predetermined location provided with a means (14) for soldering or reflow soldering; and a reflow step (24). FIG. 1.

Description

Title of the invention: Method for assembling a plurality of light-emitting diodes on a printed circuit board to form a vehicle lighting module. Technical field

[0001] The present invention relates to the field of lighting, particularly automotive lighting. The invention relates specifically to a method for assembling a plurality of light-emitting diodes (LEDs) on a printed circuit board to form a vehicle lighting module. Without limiting the scope of this invention, the lighting module can be mounted in a lighting or signaling element, and / or in a motor vehicle headlight. The lighting module is typically a lighting and / or signaling module, for example, a lighting and / or signaling module intended to be integrated into a vehicle bumper or fender to perform a daytime running light function or a regulatory lighting function, without limiting the scope of this invention.

[0002] The invention also relates to a vehicle light module obtained by such an assembly process. State of the art

[0003] In the field of automotive lighting, it is generally known to assemble several light-emitting diodes (LEDs) on a printed circuit board to form a vehicle lighting module. Such a lighting module may include, in addition to the LEDs and the printed circuit board, a grid made of flexible material. This grid is generally perforated with several openings defining patterns, the set of patterns being intended to define individual lighting patterns in the form of light pixels. The flexible material grid thus makes it possible to isolate several light pixels from one another, as well as to define a shape, style, and / or sharpness for each pixel thus isolated.

[0004] In prior art assembly methods, the light-emitting diodes (LEDs) are first fixed to the printed circuit board, typically by brazing or soldering. The flexible material grid is then applied to the printed circuit board so that it rests against the LEDs and each grid pattern extends opposite a corresponding LED. However, due to tolerance constraints in the manufacturing of the grid, and depending on the flexible material chosen for the grid, it may be necessary to adjust the grid, or even modify it. The grid is deformed to perfectly adapt to the sometimes variable spacing between the LEDs (this is to avoid misalignments and offsets). Indeed, such misalignments between the LEDs and the grid patterns, due to component tolerance constraints, can lead to degraded operation of the light module. Typically, the positioning tolerance between the LEDs and the printed circuit board is generally between 50 µm and 100 µm. However, after reflow soldering, the LED spacing increases to 100 µm. The thickness of the solder joints decreases from 120 µm before reflow soldering to 60 µm after reflow soldering, which means the grid must not compress the solder paste before reflow soldering.

[0005] Furthermore, such a deformation of the grid can induce mechanical stresses on the components of the light module, potentially damaging them. Finally, such an assembly method is likely to create collision problems between the light-emitting diodes and the inner wall of the grid (due to uncontrolled manufacturing tolerances of the grid), which can cause optical problems, assembly problems, and ultimately reliability issues with the light module.

[0006] In addition, when the grid is flexible enough to be bent together with the printed circuit board, other problems that arise are a risk of visible deformation due to the tensile strength of the top surface of the grid (which causes defects with visible and illuminated shapes), as well as additional problems of collisions between the light-emitting diodes and the inner wall of the grid.

[0007] By way of example, patent document KR 20230077201 A describes such a lighting grid for an electric vehicle to be installed at a radiator grille position on the vehicle. The grid is provided with light transmission holes, each arranged opposite a light-emitting diode (LED) which is mounted on a printed circuit board and held at regular intervals by grid-shaped separating walls on the front surface of a flexible substrate. When the light from the LED passes through the corresponding light transmission hole, the light is reflected unevenly to express the brightness due to surface emission without hot spots due to the concentration of the LED, thus providing excellent lighting quality.However, in this patent document, the assembly between the light-emitting diodes, the printed circuit board, and the grid is carried out in the same way as detailed in the previous paragraph, thus leading to the same technical drawbacks. Description of the invention

[0008] The present invention improves the situation.

[0009] An objective of the invention is to provide a method for assembling a plurality of light-emitting diodes on a printed circuit board in order to form a vehicle light module, the light module further comprising a grid made of flexible material with openwork patterns, which makes it possible to avoid any misalignment between diodes and patterns of the grid, and therefore to avoid optical problems as well as subsequent assembly and reliability issues, while offering control over the position and orientation of the light-emitting diodes with respect to the patterns of the grid and control of the risk of tilting of the light-emitting diodes with respect to the printed circuit board.

[0010] Another objective of the invention is to propose such a method, which also allows the flexible material grid to be folded together with the printed circuit board, without damaging the solder joints or welds and without causing misalignment or collision problems between the light-emitting diodes and the grid.

[0011] To this end, a first aspect of the invention relates to a method of assembling a plurality of light-emitting diodes on a printed circuit board in order to form a vehicle light module comprising, in addition to the plurality of light-emitting diodes and the printed circuit board, a grid made of flexible material, said grid being perforated in a plurality of openings defining patterns, the set of patterns being intended to define individual light patterns in the form of light pixels.

[0012] According to the invention, the method comprises a pre-positioning step of the light-emitting diodes with respect to the grid patterns, a matrix of light-emitting diodes being obtained at the end of the pre-positioning step; a positioning step of the matrix of light-emitting diodes on the printed circuit board, each light-emitting diode of the matrix of light-emitting diodes being positioned on the printed circuit board at a predetermined location provided with a means for brazing or reflow soldering; and a reflow step in order to make an electrical and mechanical connection of the light-emitting diodes of the matrix with respect to the printed circuit board.

[0013] Thanks to an assembly process configured in this way and comprising the aforementioned steps, the flexible material grid can be precisely assembled onto the array of light-emitting diodes with a very small pitch and manufacturing tolerance. This prevents any misalignment between the diodes and the grid patterns, and therefore avoids optical problems as well as subsequent assembly and reliability issues, while also providing control over the position and orientation of the light-emitting diodes relative to the grid patterns and control over the risk of tilting the light-emitting diodes relative to the printed circuit board.

[0014] According to one embodiment of the invention, the grid is made of an elastomeric material, preferably silicone.

[0015] According to one embodiment of the invention, the brazing or reflow soldering means is an adhesive and conductive paste of the type brazing alloy paste or solder or brazing paste.

[0016] According to one embodiment of the invention, the grid is provided with a plurality of grooves for pre-positioning and holding the light-emitting diodes in place. This allows for precise positioning of the light-emitting diodes (this position then does not depend on the melting of the brazing or reflow soldering means, and additional adhesive is not required), as well as preventing angular tilting of the diode components during assembly (such tilting would result in brazed joints of varying thickness, leading to a weakness in the overall reliability). Furthermore, during the reflow soldering step, if a vacuum-assisted furnace is used, the presence of such pre-positioning and holding grooves on the grid will prevent movement of the diode components during the vacuuming and re-pressurization process.Such grooves also allow for the evacuation of gases during the remelting stage or the evacuation of water (in the form of vapor) during the thermal variations inherent in the use of the part during its service life.

[0017] According to one embodiment of the invention, the patterns of the grid each have a longitudinal section of substantially rectangular, triangular or polygonal shape.

[0018] According to one embodiment of the invention, the method further comprises a step of partitioning the LED matrix into several LED subsets, the LED subsets being either identical or different from each other. This facilitates the assembly of the LEDs on the printed circuit board when the surface area to be assembled is too large, in order to constitute the entire LED matrix but with several LED subsets that are either identical or different from each other.

[0019] According to a first embodiment, the step of pre-positioning the LEDs with respect to the grid patterns comprises a first sub-step of overmolding the grid onto the printed circuit board, and a second sub-step of pre-positioning the LEDs onto an adhesive film. Furthermore, during the step of positioning the LED array onto the printed circuit board, each LED of the LED array is positioned within a perforated pattern of the grid on the printed circuit board. Such an embodiment of the invention allows This process advantageously avoids optical problems and the subsequent assembly and reliability issues associated with rigid printed circuit boards. It also allows the flexible grid to be bent along with the printed circuit board (when the latter is flexible), without damaging the solder joints or joints and without causing misalignment or collisions between the LEDs and the grid. Furthermore, the overmolding sub-step advantageously achieves a precise and fixed position of the grid patterns, eliminates variability in certain parameters due to grid manufacturing, and ensures the grid remains securely attached to the printed circuit board.

[0020] According to a second embodiment of the invention, the step of pre-positioning the light-emitting diodes with respect to the patterns of the grid comprises a first sub-step of pre-positioning the light-emitting diodes on a removable adhesive film, a second sub-step of molding the grid by compression of the flexible material on the light-emitting diodes pre-positioned on the removable adhesive film, and a third sub-step of removing the removable adhesive film.

[0021] According to an embodiment of this second variant of the invention, during the positioning step of the LED matrix on the printed circuit board, each LED of the LED matrix is ​​positioned using one or more mechanical centering pins.

[0022] According to one embodiment of this second variant of the invention, the removable adhesive film is an ultraviolet-sensitive film or a heat-sensitive film, and the third substep of removing the removable adhesive film consists of exposing the film to ultraviolet radiation or heating the film.

[0023] According to one embodiment of this second variant of the invention, during the second substep of molding the grid by compression of the flexible material onto the light-emitting diodes pre-positioned on the removable adhesive film, openings are made in the flexible material of the grid. This allows for the evacuation of gas during the remelting step or the evacuation of water (in the form of vapor) during the thermal variations inherent in the process and in the use of the product throughout its lifespan.

[0024] Another object of the invention relates to a vehicle lighting module, comprising a printed circuit board, a plurality of light-emitting diodes, and a grid made of flexible material, the vehicle lighting module being obtained by an assembly process according to the invention. The lighting module is typically a lighting and / or signaling light module, for example, a lighting light module and / or signal light intended to be integrated into a bumper or wing of a vehicle to perform a daytime display function or a regulatory lighting function, without this being limiting within the scope of the present invention.

[0025] Another object of the invention relates to a vehicle lighting and / or signaling element, in particular for a motor vehicle, comprising a light module according to the invention.

[0026] Here, "vehicle" means any type of vehicle such as a motor vehicle, a moped, a motorcycle, a warehouse storage robot, or any other machine capable of carrying at least one passenger or intended for the transport of persons or objects.

[0027] Another object of the invention relates to a vehicle headlight comprising a light module or a lighting and / or signaling element according to the invention. Brief description of the drawings

[0028] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings in which:

[0029] [Fig-1] is a schematic representation of a method for assembling a plurality of light-emitting diodes on a printed circuit board in order to form a vehicle light module, according to a first embodiment of the invention;

[0030] [Fig.2] is a schematic representation, in top view, of the luminous module obtained at the end of the process of [Fig.1];

[0031] [Fig.3] is a schematic representation, in cross-sectional view, of the light module obtained at the end of the process of [Fig.1];

[0032] [Fig.4] is a schematic representation of a method for assembling a plurality of light-emitting diodes on a printed circuit board to form a vehicle lighting module, according to a second embodiment of the invention; and

[0033] [Fig.5] is a schematic representation, in top view, of the light module obtained at the end of the process of [Fig.4]. Detailed description

[0034] The present invention relates to a method for assembling several light-emitting diodes 2 on a printed circuit board 4 to form a vehicle lighting module 6. The lighting module 6 comprises, in addition to the light-emitting diodes 2 and the printed circuit board 4, a grid made of flexible material 8. The grid 8 is perforated with several openings 10 defining patterns. The set of patterns 10 is intended to define individual lighting patterns in the form of light pixels. Each pattern 10 typically has a longitudinal section of substantially rectangular, triangular or polygonal shape, without this being limiting within the scope of the present invention.

[0035] The light-emitting diodes 2 are, for example, white light-emitting diodes, typically having a resolution of approximately 2 mm, although this is not a limitation within the scope of the present invention. The grid 8 is preferably made of an elastomeric material, preferably silicone.

[0036] The light module 6 is typically integrated into a vehicle lighting and / or signaling element or into a vehicle headlight, the latter elements not being shown in the figures for clarity. The light module 6 is typically a lighting and / or signaling light module, for example, a lighting and / or signaling light module intended to be integrated into a vehicle bumper or fender to perform a daytime running light function or a regulatory lighting function, without this being limiting within the scope of the present invention.

[0037] Figures 1 to 3 represent the assembly process according to a first embodiment of the invention.

[0038] The method includes an initial step 20 of pre-positioning the light-emitting diodes 2 with respect to the patterns 10 of the grid 8. More specifically, according to the first embodiment of the invention illustrated in [Fig. 1], the initial step 20 of pre-positioning the light-emitting diodes 2 comprises a first sub-step 201 of overmolding the grid 8 onto the printed circuit board 4. During this first sub-step 201 of overmolding the grid 8 onto the printed circuit board 4, it should be noted that there is no blocking of the luminous surface intended for the light-emitting diodes 2 (i.e., the light-emitting diodes 2 will subsequently be able to illuminate in direct illumination). The grid 8 then adheres to the printed circuit board 4.The initial step 20 of pre-positioning the LEDs 2 then includes a second sub-step of pre-positioning the LEDs 2 on an adhesive film (the latter not being shown in [Fig. 1] for clarity). A matrix 12 of LEDs 2 is obtained at the end of the initial step 20 of pre-positioning the LEDs 2.

[0039] The method then comprises a step 22 of positioning the matrix 12 of light-emitting diodes 2 on the printed circuit board 4. During this positioning step 22, each light-emitting diode 2 of the matrix 12 of light-emitting diodes 2 is positioned on the printed circuit board 4 at a predetermined location provided with a soldering or reflow soldering means 14. More specifically, according to this first embodiment of the invention, each light-emitting diode 2 of the matrix 12 of light-emitting diodes The LEDs 2 are positioned within a perforated pattern 10 of the grid 8 on the printed circuit board 4. The adhesive film on which the LEDs 2 have been pre-positioned is then removed. Preferably, the adhesive film is an ultraviolet-sensitive or heat-sensitive film, and its removal consists of exposing the film to ultraviolet radiation or heating the film. Using such an adhesive film to pre-position the LEDs 2 allows for their mass transfer onto the printed circuit board 4.

[0040] The process finally includes a final reflow step 24 to make an electrical and mechanical connection of the light-emitting diodes 2 of the matrix 12 vis-à-vis the printed circuit board 4. During this reflow step 24, the light-emitting diodes 2 / printed circuit board 4 / grid 8 assembly is typically passed through an oven with or without vacuum assistance, or through any other equivalent reflow means (with or without vacuum assistance).

[0041] As illustrated in [Fig.2], the grid 8 is advantageously provided with several gadroons 16 for pre-positioning and holding in place the light-emitting diodes 2. Each gadroon 16 typically extends in the plane of the grid 8, over a superior surface of the latter and opposite one of the motifs 10.

[0042] Figures 4 and 5 represent the assembly process according to a second embodiment of the invention.

[0043] The method includes an initial step 20 of pre-positioning the light-emitting diodes 2 with respect to the patterns 10 of the grid 8. More specifically, according to the second embodiment of the invention illustrated in [Fig. 4], the initial step 20 of pre-positioning the light-emitting diodes 2 comprises a first sub-step 203 of pre-positioning the light-emitting diodes 2 on a removable adhesive film 18. During this first pre-positioning sub-step 203, the luminous surface of the light-emitting diodes 2 is located opposite the removable adhesive film 18. The initial step 20 of pre-positioning the light-emitting diodes 2 then comprises a second sub-step 204 of molding the grid 8 by compressing the flexible material of the latter onto the light-emitting diodes 2 pre-positioned on the removable adhesive film 18.During this second substep 204 of molding the grid 8, a special mold (not shown) is used with the additional use of a non-adherent film (not shown), in order to prevent elastomeric material from covering the luminous surface of the light-emitting diodes 2. Preferably, during the second substep 204 of molding the grid 8 by compression of the flexible material on the light-emitting diodes 2 pre-positioned on the removable adhesive film 18, openings (not shown in the figures) are made in the flexible material of the grid 8.

[0044] The initial step 20 of pre-positioning the light-emitting diodes 2 finally includes a third sub-step 205 of removing the removable adhesive film 18. Preferably, the removable adhesive film 18 is an ultraviolet-sensitive film or a heat-sensitive film, and the third sub-step 205 of removing the removable adhesive film 18 consists of exposing the film 18 to ultraviolet radiation or heating the film 18. An array 12 of light-emitting diodes 2 is obtained at the end of the initial step 20 of pre-positioning the light-emitting diodes 2.

[0045] The method then includes a step 22 of positioning the matrix 12 of LEDs 2 on the printed circuit board 4. Preferably, the printed circuit board 4 is pre-assembled (with electronic components 19) on its side opposite the side on which the LEDs 2 are positioned. During this positioning step 22, each LED 2 of the matrix 12 of LEDs 2 is positioned on the printed circuit board 4 at a predetermined location equipped with a soldering or reflow soldering means 14 (the latter being screen-printed). Preferably, each LED 2 of the matrix 12 of LEDs 2 is positioned using one or more mechanical centering pins (not shown in the figures).

[0046] The process finally includes a final reflow step 24 to effect an electrical and mechanical connection of the light-emitting diodes 2 of the matrix 12 vis-à-vis the printed circuit board 4. During this reflow step 24, the light-emitting diodes 2 / printed circuit board 4 / grid 8 assembly is typically passed through a vacuum-assisted oven, or any other equivalent reflow means.

[0047] In the assembly method according to the invention, the brazing or reflow soldering means 14 is typically an adhesive and conductive paste of the solder alloy type, such as solder or brazing paste. Furthermore, the assembly method may also include an optional step of partitioning the LED matrix 12 into several subsets of LEDs 2, the LED subsets 2 being either identical or different. This partitioning step is located between the pre-positioning step of the LEDs 2 and the positioning step of the LED matrix 12, and is particularly useful when the surface to be assembled is too large.

Claims

Demands

1. A method for assembling a plurality of light-emitting diodes (2) on a printed circuit board (4) to form a vehicle light module (6), the light module (6) comprising, in addition to the plurality of light-emitting diodes (2) and the printed circuit board (4), a grid (8) made of flexible material, said grid (8) being perforated in a plurality of openings (10) defining patterns, the set of patterns (10) being intended to define individual light patterns in the form of light pixels; characterized in that the method comprises a step (20) of pre-positioning the light-emitting diodes (2) with respect to the patterns of the grid (8), an array (12) of light-emitting diodes (2) being obtained at the end of the pre-positioning step (20);a step (22) of positioning the matrix (12) of light-emitting diodes (2) on the printed circuit board (4), each light-emitting diode (2) of the matrix (12) of light-emitting diodes (2) being positioned on the printed circuit board (4) at a predetermined location provided with a means (14) for brazing or reflow soldering; and a reflow step (24) in order to effect an electrical and mechanical connection of the light-emitting diodes (2) of the matrix (12) vis-à-vis the printed circuit board (4).

2. Method according to claim 1, wherein the grid (8) is made of an elastomeric material, preferably silicone.

3. Method according to claim 1 or 2, wherein the reflow welding means (14) is an adhesive and conductive paste of the brazing alloy paste or solder or brazing paste type.

4. A method according to any one of claims 1 to 3, wherein the grid (8) is provided with a plurality of grooves (16) for pre-positioning and holding in place the light-emitting diodes (2).

5. A method according to any one of claims 1 to 4, wherein the patterns (10) of the grid (8) each have a longitudinal section of substantially rectangular, triangular or polygonal shape.

6. A method according to any one of claims 1 to 5, wherein the method further comprises a partitioning step of the matrix (12) of light-emitting diodes (2) in several subsets of light-emitting diodes (2), the subsets of light-emitting diodes (2) being identical or different from each other.

7. A method according to any one of claims 1 to 6, wherein the step (20) of pre-positioning the LEDs (2) with respect to the patterns (10) of the grid (8) comprises a first sub-step (201) of overmolding the grid (8) onto the printed circuit board (4), and a second sub-step of pre-positioning the LEDs (2) onto an adhesive film, and wherein, during the step (22) of positioning the array (12) of LEDs (2) onto the printed circuit board (4), each LED (2) of the array (12) of LEDs (2) is positioned in a perforated pattern (10) of the grid (8), on the printed circuit board (4).

8. A method according to any one of claims 1 to 6, wherein the step (20) of pre-positioning the light-emitting diodes (2) with respect to the patterns (10) of the grid (8) comprises a first substep (203) of pre-positioning the light-emitting diodes (2) on a removable adhesive film (18), a second substep (204) of molding the grid (8) by compressing the flexible material onto the light-emitting diodes (2) pre-positioned on the removable adhesive film (18), and a third substep (205) of removing the removable adhesive film (18).

9. A method according to claim 8, wherein, during the step (22) of positioning the matrix (12) of light-emitting diodes (2) on the printed circuit board (4), each light-emitting diode (2) of the matrix (12) of light-emitting diodes (2) is positioned using one or more mechanical centering pin(s).

10. A method according to claim 8 or 9, wherein the removable adhesive film (18) is an ultraviolet-sensitive film or a heat-sensitive film, and wherein the third substep (205) of removing the removable adhesive film (18) consists of exposing the film (18) to ultraviolet radiation or heating the film (18).

11. A method according to any one of claims 8 to 10, wherein, during the second substep (204) of molding the grid (8) by compression of the flexible material onto the light-emitting diodes (2) pre-positioned on the removable adhesive film (18), openings are made in the flexible material of the grid (8).

12. Vehicle light module (6), comprising a printed circuit board (4), a plurality of light-emitting diodes (2) and a grid (8) of flexible material, in which the vehicle light module (6) is obtained by an assembly process according to any one of the preceding claims.

13. Vehicle lighting and / or signaling element comprising a light module (6) according to the preceding claim.

14. Vehicle projector comprising a light module (6) according to claim 12 or a lighting and / or signaling element according to claim 13.

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