LED module and method of sealing

Abstract

This invention relates to the field of lighting modules employing light emitting diodes (LEDs), and more particularly to LED modules suitable for exposed lens plate luminaires. There is herein provided an LED module having a printed circuit board comprising at least two layers, wherein the interface between two layers at a side surface of the printed circuit board is covered by a protrusion of an optically transmissive cover plate. The same said optically transmissive cover plate is also adapted to cover at least one LED positioned in or on the printed circuit board.

Claims

1. An LED module comprising: a printed circuit board having an upper surface, a lower surface, and a side surface; the printed circuit board comprising a first layer; a second layer; and a plurality of LEDs adapted to output light from the upper surface; and an optically transmissive cover plate positioned to cover at least one of the plurality of LEDs and having at least one protrusion arranged to cover a portion of an interface between the first layer and the second layer at the side surface of the printed circuit board, wherein the first layer forms the lower surface of the printed circuit board, and comprises a first layer side surface that is at least partially inwardly inclined.

2. The LED module as claimed in claim 1, further comprising sealant positioned between the protrusion of the optical plate and the covered portion of the interface so as to prevent ingress of foreign contaminants into the said covered portion of the interface.

3. The LED module as claimed in claim 2, wherein the sealant is adapted to adhere the protrusion of cover plate to the covered portion of the interface.

4. The LED module as claimed in claim 1, wherein: the first layer comprises a metal substrate; and the second layer comprises a dielectric material.

5. The LED module of claim 1, wherein the optical plate further comprises at least one depression alongside the protrusion of the optical plate.

6. The LED module of claim 5, further comprising sealant positioned between the depression of the cover plate and the printed circuit board for sealing the cover plate to the printed circuit board.

7. The LED module of claim 1, wherein the protrusion has at least one inclined side.

8. The LED module of claim 1, wherein at least one layer is at least partially absent in the locality of the protrusion.

9. A method of sealing an LED module, wherein said LED module comprises a printed circuit board having an upper surface and at least one side surface and comprising: a first and second layer; and a plurality of LEDs adapted to output light from the upper surface, the method comprising: providing an optically transmissive cover plate comprising translucent material positioned to cover at least one of the plurality of LEDs and comprising at least one protrusion arranged to cover a portion of an interface between the first layer and the second layer at the at least one side surface of the printed circuit board; wherein the first layer forms the lower surface of the printed circuit board, and comprises a first layer side surface that is at least partially inwardly inclined.

10. The method as claimed in claim 9, further comprising: providing sealant between the protrusion of the cover plate and the covered interface so as to prevent ingress of foreign contaminants into the section of the interface between the first layer and the second layer covered by the covered area.

11. The method as claimed in claim 9, further comprising: providing at least one depression in the optical plate alongside each protrusion; providing sealant in the depression of the optical plate for sealing of the optical plate to the printed circuit board.

12. The method as claimed in claim 9, wherein the step of providing an optical plate is adapted wherein the protrusion has at least one inclined side.

13. The method as claimed in claim 9, wherein the second layer of the printed circuit board of the LED module is at least partially absent in the locality of the protrusion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

(2) FIG. 1 shows an LED module according to a first exemplary embodiment;

(3) FIG. 2 illustrates an LED module according to a second exemplary embodiment;

(4) FIG. 3 displays an LED module according to a third exemplary embodiment;

(5) FIG. 4 depicts an LED module according to a fourth exemplary embodiment;

(6) FIG. 5a illustrates an LED module according to a fifth exemplary embodiment;

(7) FIG. 5b illustrates an LED module according to a sixth exemplary embodiment;

(8) FIG. 6 displays an LED module according to a seventh exemplary embodiment;

(9) FIG. 7 shows an LED module according to an eighth exemplary embodiment;

(10) FIG. 8 illustrates an LED module according to a ninth exemplary embodiment;

(11) FIG. 9 illustrates a technique for providing electrical connection to the printed circuit board through the optical plate;

(12) FIG. 10 depicts a flowchart for a herein disclosed method of sealing an LED module; and

(13) FIG. 11 shows a mechanically fastening plug for mounting an LED module to an external support according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) The invention provides an LED module having a cover plate, wherein the cover plate is adapted to cover an interface between two layers of a printed circuit board adapted to output light.

(15) With reference to FIG. 1, a first embodiment of an LED module 1 is shown. The LED module 1 comprises a printed circuit board (PCB) 100, having a first layer 101 and a second layer 102, and a cover plate 13. There is mounted on the upper surface 105 of the PCB a first LED 110 and a second LED 111, adapted to output light from the upper surface 105 when the LED module is in use. The cover plate 13 is arranged to cover at least one of these mounted LEDs, for example, both the first 110 and second 111 LED.

(16) The cover plate 13 comprises a protrusion 15 that extends outwardly from the cover plate. The protrusion 15 is arranged to cover a portion of the interface 107 between the first layer 101 and the second layer 102, especially at a side surface 106 of the printed circuit board 100, i.e. that part of the interface which otherwise would be exposed to the ambient or surrounding atmosphere. In this and subsequent embodiments, the protrusion 15 is shown at the edge of the cover plate 13, however, it will be understood that a protrusion is not necessarily limited to being provided at the perimeter but may, for example, be provided inward of the perimeter of the cover plate 13.

(17) Sealant 14 is positioned between the cover plate 13 and the portion of the interface 107 covered by the protrusion 15 of the cover plate. In the present embodiment, the sealant 14 extends to partially cover the upper surface of the printed circuit board 100. By sealing the cover plate to the printed circuit board with sealant in this manner, the portion of the interface 107 covered may be sealed to prevent ingress of foreign contaminants. Thus, the interface between the first layer 101 and the second layer 102 may be protected from contaminants such as water, dust or other particles.

(18) Optionally, the sealant may be adhesive so as to stick the optical plate to the PCB 100.

(19) The first layer 101 may be a substrate, such as an metal substrate (e.g. aluminium). The second layer 102 may be a dielectric material (e.g. silicon) upon which a LED may be formed or mounted. The second layer 102 may in some other embodiments be an epoxy or polyimide material. The layers may otherwise or additionally comprise other materials, such as epoxy impregnated glass fabric or even an electrically insulating material with integrated copper tracks.

(20) A second embodiment of an LED module 2 is shown in FIG. 2. The LED module 2 similarly comprises a PCB 200, having a first layer 201 and a second layer 202, and a cover plate 23. The cover plate 23 is arranged to cover at least one LED (not shown) mounted on the upper surface 205 of the printed circuit board 200.

(21) As in the first embodiment, the cover plate 23 comprises a protrusion 21 arranged to cover a portion of the interface between the first layer 201 and the second layer 202. Sealant 24 is positioned between at least the protrusion 21 of the cover plate 23 and the PCB 200 to seal the covered portion of the interface against foreign contaminants.

(22) In this second embodiment, the cover plate 23 further comprises a depression 25 alongside the protrusion 21. The depression 25 may be a groove in the cover plate 23 that runs alongside the length of the protrusion 21. The sealant 24 is extended to at least partially fill the depression 25 so as to seal the cover plate to the upper surface of the printed circuit board. The provision of a depression 25, alternatively named a channel, in this manner may accommodate relative movement between the optical plate and the printed circuit board when the LED module is in use.

(23) A third embodiment of an LED module 3 is illustrated in in FIG. 3. The LED module 3 comprises the same features as the second embodiment exhibited in FIG. 2. That is to say, a PCB 300, having a first layer 301 and a second layer 302, wherein the interface between the said two layers is covered by a protrusion 35 of a cover plate 33. Sealant 34 positioned between the cover plate 33 and the printed circuit board helps prevent ingress of foreign contaminants into the covered portion of the interface.

(24) In the present embodiment, however, a side 351 of the protrusion 35 of the cover plate 33 is partially inclined. In other words, the protrusion 35 slightly tapers in the direction away from the body of the optical cover 33. To incline the protrusion in this manner may enable the sealant 34 to be positioned with greater ease.

(25) Another embodiment of an LED module 4, shown in FIG. 4, comprises all the features of the third embodiment exhibited in FIG. 3. In other words, an inclined protrusion of an optical plate 43 is arranged to cover an interface formed between a first layer 401 and second layer 402 of a PCB 400. Sealant 44 is positioned between the optical plate 43 and the PCB 400 to seal the aforementioned interface from foreign contaminants.

(26) In this fourth embodiment, the edges of the PCB 400 are inwardly inclined, that is to say at least partially inclined in the direction of the body of the printed circuit board. Thus the area of the upper surface 405 of the PCB 400 may be smaller than the area of a lower surface 406 of the printed circuit board. Providing an inclined side of the printed circuit board in this manner may permit improved sealant flow during provision of the said sealant.

(27) In a fifth embodiment of the LED module 5a, illustrated by FIG. 5a, the features of the fourth embodiment are present. Thus, the PCB 500 comprises a first layer 501 and a second layer 502. The interface formed at the edge of the printed circuit board between the first layer 501 and the second layer 502 is at least partially covered by a protrusion 55 of an optical plate 53. Sealant 54 is positioned between at least a protrusion 55 and the edge of the printed circuit board such that the interface between the first 501 and second 502 layer is at least partially sealed against the admission of contaminants between the layers. In this specific case where part of the layer 502 is removed, it is not necessary that the protrusion 55 or the sealant extends to the side of the PCB. They can also be restricted to the top surface to be directly connected to the metal of the PCB.

(28) The second layer 502 of the fifth embodiment is adapted to be partially absent in the locality of the protrusion 55. In some embodiments, therefore, the second layer 502 may be partially removed in the immediate vicinity of the protrusion 55. Thus the second layer 502 of the PCB 500 may be partially absent towards the edge or perimeter of the printed circuit board 500. The partial absence of the second layer may allow for improved sealing of the cover plate to the first layer, which may, for example, be stuck by adhesive sealant with greater adherence than the second layer.

(29) Another embodiment of an LED module 5b is shown in FIG. 5b. Similar to the fifth embodiment of FIG. 5a, the LED module comprises a printed circuit board 5000 comprising a first layer 5001 and a second layer 5002. An optical cover plate 5003 is arranged to cover at least one LED (not shown) positioned on the top of the second layer 5002. A protrusion 5005 of the optical cover plate 5003 is arranged to cover the interface between the first layer 5001 and the second layer 5002. Sealant is positioned between the first layer 5001 and the second layer 5002 to sealably adhere the optical cover plate to the printed circuit board.

(30) The second layer 5002 of the present embodiment is adapted to be partially absent in the locality of the protrusion 5005. In the present embodiment the absence 5004 of the second layer 5002 is partially inward to the printed circuit board 5000. The partial absence of the second layer may allow for improved sealing of the cover plate 5003 to the first layer 5001, which may, for example, be stuck by adhesive sealant 5004 with greater adherence than the second layer 5002.

(31) A seventh embodiment of an LED module 6 is shown in FIG. 6. Again, the LED module comprises a printed circuit board 600 covered at an edge by a protrusion of an optical plate 63 such that an interface between a first 601 and second 602 layer is at least partially covered. An LED 610, positioned on an upper surface of the printed circuit board 600, is covered by the optical plate 63. A first depression 65 is present in the optical plate 63 alongside the protrusion.

(32) The optical plate 63 further comprises a second depression or channel 66 alongside the first depression 65. In the event that sealant 64 of a sufficiently low viscosity may otherwise flow into the flat area of the printed circuit board a second depression 66, for example a groove or channel in the optical plate, can function as a trap to prevent flow towards the LEDs, for example the LED 610.

(33) With reference to FIG. 7, an eighth embodiment of an LED module 7 may be seen. The LED module comprises a PCB 700 having a first layer 701 and a second layer 702. An LED 710 is mounted upon the upper surface of the printed circuit board adapted to emit light. An optical plate 73, positioned to cover the LED 710, comprises a protrusion 75 arranged to cover the interface between the first 701 and second layer 702 at the edge of the PCB 700.

(34) A sealing mould 74, made of a plastic material such as silicone rubber, is attached to both the PCB 700 and the protrusion 75 of the optical plate 73. The sealing mould may be attached by a known overmolding or a known 2k molding process. Thus, the portion of the interface covered by the protrusion 75 between the first 701 and second layer 702 may be sealed against the ingress of foreign contaminants by the sealing mould 74. Preferably the sealing mould 74 does not extend to cover the lowermost surface 706 of the PCB 700.

(35) Another embodiment of an LED module 8 is illustrated in FIG. 8. As before, the LED module comprises a PCB 800 having a first layer 801 and a second layer 802. A optically transmissive cover plate 83 is positioned to cover at least one LED 810 (positioned on an upper surface 805 of the PCB 800) and comprises a first protrusion 85 arranged to cover a portion of an interface between the first layer 801 and the second layer 802 at a side surface of the PCB 800. Sealant 84 is positioned between the first protrusion 85 and the side surface of the printed circuit board such that the portion of the interface between the first layer 801 and the second layer 802 covered by the protrusion is sealed against foreign contaminants.

(36) The present embodiment, however, further comprises an additional protrusion 87. The additional protrusion protrudes outwardly from the cover plate to cover a section of the upper surface 805 of the PCB 800. Additional sealant 86 is provided between the additional protrusion 87 and the upper surface 805 of the PCB 800 to seal the optical plate 83 to the printed circuit board 87. The sealant may be adhesive, and thereby fix the optical plate to the upper surface of the PCB 800. The additional sealant may be called an upper surface sealing protrusion. By providing at least one such upper surface sealing protrusions, an area of the upper surface of the printed circuit board, which may contain at least one LED 810, may be protected against the ingress of foreign contaminants.

(37) Presented in FIG. 9 is a technique for providing a feed-through for wires through a protrusion 900 to allow, for example, provision of an external power supply to the LEDs. The exemplary protrusion 900 is an upper surface sealing protrusion, such as the additional protrusion 87. This should not be construed as limiting the feed-through of wires to only apply to an upper surface sealing protrusion, but may rather also apply to the side-sealing protrusions such as those embodied in FIGS. 1-7.

(38) For provision of wires through the protrusion 900a cavity 905, for example a channel or depression, is provided 990 in the protrusion. Such a cavity spans across the width of the protrusion, for example, in a substantially perpendicular direction to that of the length of the protrusion. Optionally, the cavity 905 may have a variable width over the length of the said cavity. Sealant 920 is provided 991 in the cavity, to which a wire 910 is sunk. A printed circuit board 950 is provided 992 and brought into contact 993 with the protrusion 900. The sealant thereby seals the wire 910 within the cavity 920, and partially seals the circuit board 950 to the protrusion 900. In the present embodiment there is only sufficient sealant 920 to completely fill the cavity 905 such that within the cavity 905 (including the wire 910) there are no gaps or voids. Thus wires may be provided to the printed circuit board from an external (to the present LED module) interface.

(39) With reference to FIG. 10, a method 10 of sealing an LED module 1000 is illustrated. The method comprises: providing an optically transmissive cover plate comprising translucent material positioned 1002 to cover at least one of the plurality of LEDs and comprising at least one protrusion arranged 1003 to cover a portion of an interface between the first layer and the second layer at the at least one side surface of the printed circuit board. The method may further comprise providing 1005 sealant between the protrusion of the cover plate and the covered interface so as to prevent ingress of foreign contaminants into the section of the interface between the first layer and the second layer covered by the covered area. An additional optional method step comprises providing 1004 at least one depression in the optical plate alongside each protrusion and providing sealant in the depression of the optical plate for sealing of the optical plate to the printed circuit board.

(40) A cross-section of one embodiment of a mechanical fixation plug 1130 for securing the LED module 1110, 1120 into an external support 1150 is shown in FIG. 11. The LED module comprises the printed circuit board 1110 and the optical plate 1120, which in this embodiment lie substantially flat and flush against one another.

(41) The plug 1130 spans through both the printed circuit board 1110 and the optical plate 1120 without extending beyond a bottom surface 1111 of the printed circuit board. A mechanical fastener 1140, for example a screw, is mountable within the plug for affixing the plug to the external support 1150 which may, for example, be a ceiling, wall or another part of the luminaire (such as a heatsink or housing).

(42) To secure the plug to LED module, the plug 1130 comprises at least one clamp 1133 which may extend in a single direction (for example the X-direction along the length of the LED module). The plug 1130 has a press module 1134 for ensuring the bottom surface 1111 of the printed circuit board is made to lie substantially flat against the external support 1150. The mechanical screw 1140 applies direct pressure to the printed circuit board 1110, through the press module 1134, to perform this action. In embodiments the press module may extend in the Z-direction (i.e. into the page, at least partially spanning the width of the LED module). The plug 1130 further comprises at least one wing 1131 which spans across an exposed surface of the optical plate to mechanically secure the optical plate to the printed circuit board. The wing may comprise a wing protrusion or pin 1132 which projects into the optical plate for a more secure fastening. The optical plate may thus be pushed against the printed circuit board. In some embodiments the wing 1131, inclusive of a wing protrusion 1132, may be thought to function as a spring, and may permit movement in the Z-Direction and the X-direction (i.e. the direction corresponding to the width and length of the LED module), but may limit movement in the Y direction. Thus the optical plate 1120 may be kept a constant distance from the printed circuit board 1130.

(43) Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.