Abstract
The invention refers to a method for assembling at least one lighting element onto a substrate, the method comprising: pre-assembling at least one lighting element onto a temporary carrier; pre-assembling at least one reference element onto the temporary carrier; aligning the pre-assembled temporary carrier onto the substrate based, at least in part, on the at least one reference element of the temporary carrier; and mounting the at least one lighting element onto the substrate. The invention further relates to substrate comprising: at least one lighting element, wherein the at least one lighting element is assembled onto the substrate, in particular by a method according to the first aspect of the present invention, and to a use of a method for assembling at least one lighting element onto a substrate.
Claims
1. A method for assembling at least one lighting element (22) onto a substrate (40), comprising: pre-assembling at least one lighting element (22) onto a temporary carrier (10) that is or comprises a tape; pre-assembling at least one reference element (30) onto the temporary carrier (10), the at least one reference element (30) having an equal or greater thickness as the at least one lighting element (22) and providing a mechanical stop for aligning the pre-assembled temporary carrier (10) in at least one direction, the at least one reference element (30) comprising at least one fiducial providing a mechanical stop for aligning the pre-assembled temporary carrier (10) in a third direction and/or for enabling optical alignment of the pre-assembled temporary carrier (10); aligning the pre-assembled temporary carrier (10) onto the substrate (40) based, at least in part, on the at least one reference element (30) of the temporary carrier (10); and mounting the at least one lighting element (22) onto the substrate (40).
2. The method according to claim 1, further comprising: removing the temporary carrier (10) from the substrate (40) when the at least one lighting element (22) is permanently attached to the substrate (40).
3. (canceled)
4. The method according to claim 1, wherein the at least one fiducial is a dent or recess on a top side of the at least one reference element (30).
5. The method of claim 1, wherein the at least one reference element (30) at least temporarily fixes the at least one lighting element (22) during its mounting in relation to the substrate by at least two degrees of freedom.
6. The method according to claim 1, wherein the pre-assembled temporary carrier (10) is aligned to the substrate (40) by a pick and place process (60).
7. The method according to claim 1, wherein the substrate (40) is a printed circuit board.
8. The method according to claim 1, wherein the at least one lighting element (22) is mounted to the substrate (40) by gluing or soldering it onto the substrate (40).
9. The method according to claim 1, further comprising: mounting the at least one reference element (30) onto the substrate (40) prior to or after the mounting of the at least one lighting element (22).
10. The method according to claim 1, wherein the temporary carrier (10) comprises an adhesive layer (12) enabling the pre-assembling of the at least one lighting element (22) and the at least one reference element (30) onto the temporary carrier (10).
11. The method according to claim 1, wherein a plurality of lighting elements (22) are pre-assembled onto the temporary carrier (10) in a single or M×N array structure (20).
12. The method according to claim 1, wherein the at least one reference element (30) is a frame (32, 34) that enables alignment of at least one optical element (70, 72, 76) to the substrate (40).
13. A substrate (40) comprising: at least one lighting element (22), wherein the at least one lighting element (22) is assembled onto the substrate (40) by a method according to claim 1.
14. The substrate (40) according to claim 13, wherein the substrate (40) is a printed circuit board.
15. Use of a method according to claim 1 for assembling optical components with one or more lighting elements (22).
16. The method according to claim 1, wherein the temporary carrier (10) comprises a foil (14).
17. The method according to claim 1, wherein mounting the at least one lighting element (22) onto the substrate (40) comprises reflow soldering the at least one lighting element (22) onto the substrate (40).
18. The method according to claim 1, further comprising reflow soldering the at least one reference element (30) to the substrate (40).
19. The method according to claim 1, wherein aligning the pre-assembled temporary carrier (10) onto the substrate (40) comprises aligning each of the at least one lighting element (22) and the at least one reference element (30) to solder paste (44) coated on the substrate (40).
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Examples of the invention will now be described in detail with reference to the accompanying drawing, in which:
[0039] FIG. 1a shows a schematic representation of an embodiment of a temporary carrier in a cross-sectional view;
[0040] FIG. 1b shows the schematic representation of FIG. 1a of the embodiment of the temporary carrier in a top view;
[0041] FIG. 2 shows a schematic representation of a pre-assembled temporary carrier to be mounted to a structure in a cross-sectional view;
[0042] FIG. 3a shows a schematic representation of another pre-assembled temporary carrier to be mounted to a structure in a cross-sectional view;
[0043] FIG. 3b shows the schematic representation of FIG. 3a in a top view;
[0044] FIG. 4 shows a schematic representation of another pre-assembled temporary carrier to be mounted to a structure in a cross-sectional view;
[0045] FIG. 5a shows a schematic representation of another pre-assembled temporary carrier to be mounted to a structure in a cross-sectional view;
[0046] FIG. 5b shows the schematic representation of FIG. 5a in a top view;
[0047] FIG. 6a shows a schematic representation of an assembled structure with an optical element in a cross-sectional view;
[0048] FIG. 6b shows a schematic representation of an assembled structure with another, second optical element in a cross-sectional view;
[0049] FIG. 6c shows a schematic representation of an assembled structure with another, third optical element in a cross-sectional view;
[0050] FIG. 7a-7d show schematic representations of assembled structures with different aligned objects; and
[0051] FIG. 8 shows a schematic representation of an embodiment of a temporary carrier in a top view enabling alignment in two directions.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0052] FIG. 1a shows a schematic representation of a first embodiment of a temporary carrier 10 in a perspective view. Onto the temporary carrier 10, two reference elements 30-1 and 30-2 are mounted, e.g. attached to a sticky tape. Further, a lighting element array 20 is attached to the temporary carrier 10. In FIG. 1a, four lighting elements 22-1 to 22-4 of the 2x4 lighting element array 20 are viewable. For attaching the reference elements 30-1 and 30-2 and the lighting element array 20 to the temporary carrier 10, an adhesive layer 12 is comprised by the temporary carrier 10. The top side of the temporary carrier 10 may be a foil 14 (see e.g. FIG. 5b), which can be removed (e.g. peeled off).
[0053] FIG. 1b shows the schematic representation of FIG. 1a of the embodiment of the temporary carrier 10 in a top view. It can be seen that the two reference elements 30-1 and 30-2 are of circular shape and are located on the left and the right side of the 2×4 lighting element array 20. The two reference elements 30-1 and 30-2 provide a mechanical stop for the pre-assembled temporary carrier 10 with the lighting element array 20 when the lighting elements 22 of the lighting element array 20 are to be mounted to a substrate 40 (see e.g. FIG. 2). As an alternative to the 2×4 lighting element array 20, a single lighting element (e.g. LED die emitter), or a M×N array may be comprised by or attached to the temporary carrier 10. For instance, for the application of a Luxeon NEO Exact, the lighting elements of such a lighting element array may be spaced closely or positioned in close relation to each other. Further, e.g. for the application of a Luxeon Neo, the lighting elements of such a lighting element array may be spaced widely or positioned in a wider relation compared to the aforementioned case to each other.
[0054] The temporary carrier 10 as described above may form a pre-assembly structure, as disclosed above. This pre-assembly structure can be used by customers as standard SMD component, supplied in tape and reel packing and can be assembled with SMT machines and reflow soldering to PCBs or isolated metal substrates (IMS), to name but a few non-limiting examples. The mechanical reference elements 30-1 and 30-2 can be soldered to the PCB copper surface (solder pads) at the same time.
[0055] FIG. 2 shows a schematic representation of a pre-assembled temporary carrier 10 to be mounted to a structure 40 in a cross-sectional view. The lighting elements 22 attached to the temporary carrier 10 are to be mounted (e.g. soldered) to the substrate 40. The position at which the lighting elements 22 of the lighting element array 20, and the two reference elements 30-1 and 30-2 are to be mounted, solder paste 44 is applied. The substrate 40 has a copper trace on its top side to which e.g. the lighting elements 22 and/or the reference elements 30 can be soldered. Further, at sections of the substrate 40 to which an attaching of e.g. the lighting elements 22 and/or the reference elements 30 should be avoided, a respective solder mask 46 is applied. As indicated by the arrow 60, the temporary carrier 10 comprising the lighting elements 22 and the reference elements 30 can be positioned in its intended position in relation to the substrate 40. Then, e.g. by a reflow soldering, the lighting elements 22 and/or the reference elements 30 are soldered to the substrate 40. Thus, this pick and place process 60 can be used to manufacture a structure comprising one or more elements, e.g. the lighting elements 22 that are mounted (here: soldered) to the substrate 40 via utilizing the temporary carrier 10. The substrate 40 may be a PCB.
[0056] FIG. 3a shows a schematic representation of another pre-assembled temporary carrier 10 to be mounted to a structure in a cross-sectional view. In comparison to the temporary carrier 10 of the embodiments shown in FIGS. 1a, 1b and 2, the reference element is a frame 32. The frame 32 may for instance be used to mount one or more optical elements, such as a reflector or a lens to the frame 32, and/or using the frame 32 to align one or more of such optical elements in relation to the substrate 40. The mounting of the lighting elements 22 and/or of the frame 32 may be performed in the same way as described above.
[0057] FIG. 3b shows the schematic representation of FIG. 3a in a top view. It can be seen that the frame 32 surrounds the lighting element array 20 (at present a 2×4 LED array) at all sides. The frame 32 comprises a cut-out section in which the lighting element array 20 can be attached. The frame 32 comprises vertical side walls extending beyond the top surface of the temporary carrier 10. The vertical side walls may for instance be used for aligning and/or mounting one or more optical elements, such as a reflector or a lens to the frame 32.
[0058] FIG. 4 shows a schematic representation of another pre-assembled temporary carrier 10 to be mounted to a structure 40 in a cross-sectional view. The substrate 40 which is to be mounted with the lighting elements array 20 comprised by the temporary carrier 10, has glue 50 attached to it at positions, where the reference elements 30-1 and 30-2 are to be glued to. Further, at positions, where the lighting elements 22 of the lighting element array 20 are to be mounted, solder paste 44 is coated. The reference element 30-2 may have a fiducial that can be used for optical recognition, e.g. enabling to align the temporary carrier 10 to a reference hole 52 that is drilled into the substrate 40. The fiducial cannot be seen in the FIG. 4 since it is a dent/recess on the top side of the reference element 30-2. It will be understood that such a fiducial can be comprised by the reference element 30-1, or be comprised as a dent/recess on the top side shown in FIG. 4 of the temporary carrier 10, too. The pick and place process 60 can utilize such fiducials and/or reference holes 52.
[0059] FIG. 5a shows a schematic representation of another pre-assembled temporary carrier to be mounted to a structure in a cross-sectional view. FIG. 5b shows the schematic representation of FIG. 5a in a top view. The temporary carrier 10 comprises a temporary frame 34 as one of its reference elements. Further reference elements comprised by the temporary carrier 10 are the reference elements 30-1 and 30-2 of circular shape. A foil 14 of the temporary carrier 10 having an adhesive layer ensures that the reference elements 30-1, 30-2 and 34 at least temporary stick to the temporary carrier 10, e.g. until the lighting element array 20 also comprised by the temporary carrier 10 are mounted to the substrate. The temporary frame 34 may for instance be removed from the substrate after the lighting element array 20 is successfully mounted to the substrate. The temporary frame 34 at least temporarily fixes the lighting element array 20 during the mounting process in relation to the substrate by at least two degrees of freedom.
[0060] Such a frame 34 increases the stability of the temporary carrier 10, in particular of a foil 14 comprised by the temporary carrier 10. This further increases the tolerances for warping and the like, that may occur during the mounting of at least the lighting elements onto a substrate.
[0061] FIG. 6a to FIG. 6b show schematic representation of an assembled structure (e.g. final product representing a sub-element for an automotive headlamp) with three different optical elements mounted to the substrate 40 in a cross-sectional view. In FIG. 6a, it can be seen that the circular reference elements 30-1 and 30-2 are also used to align the optical element 70 to the substrate. At present, the optical element is a pre-optic 70. The pre-optic comprises light guides aligned in relation to the lighting elements 22 of the lighting element array 20 enabling that the lighting elements 22 can emit light at least in a direction as defined by the light guides.
[0062] The optical element 72 shown FIG. 6b also utilizes the circular reference elements 30-1 and 30-2: the optical element 72 has a certain shape allowing it to snap-in beneath the reference elements 30-1 and 30-2. Thus, the optical element 70 is also a pre-optic, wherein it comprises at least one hook-shaped ending allowing the optical element to be attached to the substrate by snapping-in under the circular reference elements 30-1 and 30-2. The reference elements 30-1 and 30-2 are mounted to the substrate 40 in a fixed manner so that the reference elements 30-1 and 30-2 cannot be removed during normal usage.
[0063] The embodiment shown in FIG. 6c additionally comprises a guide frame 74 for additional alignment of the optical element 70 (at present: a pre-optic). The guide frame 74 is aligned and mounted to the reference elements 30-1 and 30-2 that are permanently mounted to the substrate 40. The light guides aligned in relation to the lighting elements 22 of the lighting element array 20 may for instance utilize the guide frame 74, so that the pre-optic 70 is also aligned by the guide frame 74. The guide frame 74 may be a metal sheet with one or more holes allowing the light guides of the pre-optic 70 to penetrate the holes. Thus, the holes enable additional alignment of the pre-optic 70.
[0064] FIG. 7a to FIG. 7d show schematic representations of assembled structures with different aligned objects. The reference element 30 of FIG. 7a is used to align the object 76 in at least two directions. It can be seen that the object 76 is in no direct contact with the substrate 40. The object 76 has a recess of a shape corresponding to the reference element 30, e.g. a circular recess. Thus, such a recess of the object 76 to be aligned may form-fit to the reference element 30. The aligned object 76 of FIG. 7b has a protruding section that can be put through a reference element that has a corresponding hole, and that is mounted (e.g. soldered) to the substrate 40. The aligned object 76 of FIG. 7c has a snap-in geometry so that the object 76 can snap-in beneath of the reference element 30. The reference element 30 is mounted (e.g. soldered) to the substrate 40 permanently. The object 76 of FIG. 7d is aligned by a pin 78 that penetrates both a hole of the object 76 and a hole comprised by the reference element 30. The reference element 30 is permanently mounted (e.g. soldered) to the substrate 40. It can be seen that the reference element as disclosed in the present invention can serve further alignment purposes besides providing enhanced ease of mounting of the lighting element(s) to a substrate, e.g. by preventing tilting of lighting element(s) during the mounting (e.g. soldering and/or gluing).
[0065] FIG. 8 shows a schematic representation of an embodiment of a temporary carrier 10 in a top view enabling alignment in two directions. The temporary carrier 10 has four reference elements, two of them (reference elements 30-3) for enabling alignment in Y-direction, and two of them (reference elements 30-4) for enabling alignment in X-direction. For illustrative purpose, the X- and Y-axis are drawn in FIG. 8.
[0066] Further, the temporary carrier 10 comprises a frame 32 that enables alignment of a geometry at an optical element (e.g. optics). In the middle of the frame 32, at present a 2×4 lighting element array 20 is attached to the temporary carrier. The attachment of the lighting elements 22 of the lighting element array 20, and of the reference elements 30-3 and 30-4 may be done in the same way as disclosed above.
[0067] The temporary carrier as disclosed in example embodiments according to all aspect may represent a L1 or a L2 element. A level 1 element has this temporary carrier with a mechanical reference as a corresponding reference element, and/or a level 2 element which has used this type of assembly method, enable a characteristic positional pattern where the tolerance between the lighting element(s), e.g. LEDs and one or more optical elements (e.g. optics) is enhanced. Further, putting such a substrate, e.g. a level 2 element a second time through a reflow soldering process may cause even more enhanced alignment of the lighting elements (e.g. LEDs) due to additional self-centering effects happening during the second reflow soldering.
[0068] The optical element(s) could also be shutter or sheet masks (e.g. cut-off or strip masks), which have optical functionality. Additionally or alternatively, the optical element(s) may be connecting elements providing a possibility to mount or attach one or more optics (e.g. reflector or lens) to the connecting element(s). Thus, at such a connecting element, an optical element (e.g. reflector or lens) can be aligned or referenced to.
REFERENCE SIGNS
[0069] 10 temporary carrier
12 adhesive layer
14 foil
20 lighting array
22 lighting element
30 reference element
32 reference element: frame
34 reference element: temporary frame
40 substrate
42 solder contact
44 solder paste
46 solder mask
48 copper trace
50 glue
52 reference hole
60 pick and place process
70 optical element: pre-optics
72 optical element: pre-optics for snap-in mounting
74 guide frame for alignment of optical element
76 aligned object
78 pin
