LED FILAMENT WITH HEAT SINK

Abstract

A light emitting diode, LED, filament (110), configured to emit LED filament light, comprising an array of a plurality of light emitting diodes (120), LEDs, configured to emit LED light, a carrier (130) arranged to support the plurality of LEDs, at least one heat sink (140) arranged in thermal connection with the carrier for a dissipation of heat from the plurality of LEDs during operation, wherein the at least one heat sink comprises a base portion (150) extending parallel to the carrier, and a plurality of fins (160) projecting from the base portion, and an encapsulant (170) comprising a translucent material, wherein the encapsulant at least partially encloses the plurality of LEDs, the carrier and the at least one heat sink.

Claims

1. A light emitting diode, LED, filament, configured to emit LED filament light, comprising an array of a plurality of light emitting diodes, LEDs, configured to emit LED light, a carrier arranged to support the plurality of LEDs, at least one heat sink arranged in thermal connection with the carrier for a dissipation of heat from the plurality of LEDs during operation, wherein the at least one heat sink comprises a base portion extending parallel to the carrier, and a plurality of fins projecting from the base portion, and an encapsulant comprising a translucent material, wherein the encapsulant at least partially encloses the plurality of LEDs, the carrier and the at least one heat sink, wherein the at least one heat sink comprises a metal foil.

2. The LED filament according to claim 1, wherein the plurality of fins of the at least one heat sink constitutes folds of the base portion of the at least one heat sink.

3. The LED filament according to claim 1, wherein the plurality of LEDs is arranged on a first side of the carrier, and one heat sink of the at least one heat sink is arranged on a second side of the carrier, opposite the first side of the carrier.

4. The LED filament according to claim 1, wherein the plurality of LEDs and one heat sink of the at least one heat sink are arranged on a first side of the carrier.

5. The LED filament according to claim 1, wherein the base portion of the at least one heat sink comprises a plurality of apertures configured to transmit at least part of the LED filament light through the plurality of apertures.

6. The LED filament according to claim 1, wherein the at least one heat sink comprises at least one of copper, Cu, and aluminum, Al.

7. The LED filament according to claim 1, wherein the at least one heat sink further comprises a layer comprising at least one of an electrically insulating material, whereby the layer constitutes an electrical insulation layer, and a reflective material, whereby the layer constitutes a reflective layer having a higher reflectivity than the base portion of the at least one heat sink.

8. The LED filament according to claim 1, wherein the encapsulant completely encloses the at least one heat sink.

9. The LED filament according to claim 1, wherein the plurality of fins of the at least one heat sink protrudes the encapsulant and extends from the encapsulant.

10. The LED filament according to claim 1, wherein the encapsulant comprises at least one of a light-scattering material configured to scatter light emitted from the plurality of LEDs and a luminescent material configured to at least partly convert light emitted from the plurality of LEDs into converted light.

11. The LED filament according to claim 1, wherein the encapsulant and the at least one heat sink are flexible.

12. The LED filament according to claim 1, wherein the encapsulant comprises silicone.

13. The LED filament according to claim 1, wherein the base portion of the at least one heat sink comprises a plurality of apertures configured to transmit at least part of the LED filament light through the plurality of apertures, wherein the encapsulant comprises at least one of a light-scattering material configured to scatter light emitted from the plurality of LEDs and a luminescent material configured to at least partly convert light emitted from the plurality of LEDs into converted light, wherein the encapsulant is flexible and the at least one heat sink is flexible, and wherein the LED filament has at least one of a spiral, meander, coil and helix shape.

14. A LED lighting device, comprising at least one LED filament according to claim 1, a cover comprising an at least partially transparent material, wherein the cover at least partially encloses the LED filament, and an electrical connection connected to the LED filament for a supply of power to the plurality of LEDs of the LED filament.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

[0032] FIG. 1 schematically shows a LED filament lamp according to the prior art, comprising LED filaments,

[0033] FIG. 2a schematically shows a LED filament according to an exemplifying embodiment of the present invention,

[0034] FIG. 2b schematically shows a heat sink of a LED filament according to an exemplifying embodiment of the present invention,

[0035] FIGS. 2c and 2d schematically show a LED filament according other exemplifying embodiments of the present invention,

[0036] FIGS. 3a-3c schematically show a provision of a heat sink of a LED filament according to an exemplifying embodiment of the present invention, and

[0037] FIG. 4 schematically shows a LED light device according to an exemplifying embodiment of the present invention.

DETAILED DESCRIPTION

[0038] FIG. 1 shows a LED filament lamp 10 according to the prior art, comprising a plurality of LED filaments 20. LED filament lamps 10 of this kind are highly appreciated as they are very decorative, as well as providing numerous advantages compared to incandescent lamps such as a longer operational life, a reduced power consumption, and an increased efficiency related to the ratio between light energy and heat energy.

[0039] FIG. 2 schematically shows a LED filament 110 according to an exemplifying embodiment of the present invention. The LED filament 110, which elongates along the axis, A, is configured to emit LED filament light. The LED filament 110 may preferably have a length, L.sub.f, in the range from 1 cm to 20 cm, more preferably 2 cm to 12 cm, and most preferred 3 cm to 10 cm. The LED filament 110 may preferably have a width, W.sub.f, in the range from 0.5 mm to 10 mm, more preferably 0.8 mm to 8 mm, and most preferred 1 to 5 mm. The aspect ratio L.sub.f/W.sub.f is preferably at least 5, more preferably at least 8, and most preferred at least 10.

[0040] The LED filament 100 comprises an array or chain of a plurality of LEDs 120 configured to emit LED light. For example, the array or chain of the plurality of LEDs 120 may comprise a plurality of adjacently arranged LEDs 120 wherein a respective wiring is provided between each pair of LEDs 120. The plurality of LEDs 120 preferably comprises more than 5 LEDs, more preferably more than 8 LEDs, and even more preferred more than 10 LEDs. The plurality of LEDs 120 may be direct emitting LEDs which provide a color. The LEDs 120 are preferably blue LEDs. The LEDs 120 may also be UV LEDs. A combination of LEDs 120, e.g. UV LEDs and blue light LEDs, may be used. The LEDs 120 may comprise laser diodes. The LED filament light emitted from the LED filament 110 during operation is preferably white light. The white light is preferably within 15 SDCM from the black body locus (BBL). The color temperature of the white light is preferably in the range of 2000 to 6000 K, more preferably in the range from 2100 to 5000 K, most preferably in the range from 2200 to 4000 K such as for example 2300 K or 2700 K. The white light has preferably a CRI of at least 75, more preferably at least 80, most preferably at least 85 such as for example 90 or 92.

[0041] The LED filament 110 further comprises a carrier 130 arranged to support the plurality of LEDs 120. The plurality of LEDs 120 may be arranged, mounted and/or mechanically coupled on/to the carrier 130. The carrier 130, e.g. a substrate, is configured to mechanically and/or electrically support the plurality of LEDs 120. The carrier 130 may be a printed circuit board (PCB). The carrier 130 may be light transmissive and/or reflective. Furthermore, the carrier 130 may be flexible, and may for example comprise a polymer foil (e.g. polyimide (PI), polyethylene terephthalate (PET), etc.). The carrier 130 may comprise one or more thermally conductive layers and one or more insulating layers.

[0042] The LED filament 110 further comprises at least one heat sink 140, wherein a single heat sink 140 is exemplified in FIG. 2a. The heat sink 140 is arranged adjacent the carrier 130 and is arranged in thermal connection with the carrier 130 for a dissipation of heat from the plurality of LEDs 120 during operation of the LED filament 100. The heat sink 140 may be arranged in physical (direct) contact with the carrier 130. It should be noted that the heat sink 140 may constitute and/or have the form of substantially any structure, component, arrangement, or the like, which is configured and/or arranged to dissipate heat. The heat sink 140 comprises a base portion (not indicated/shown in FIG. 2a for reasons of visibility) extending parallel to the carrier 130. It should be noted that the carrier in FIG. 2a is elongated in order to support the array of LEDs 120 of the (elongated) LED filament 100, and the base portion of the heat sink 140 is hereby also elongated. The heat sink 140 further comprises a plurality of fins 160 projecting from its base portion. Albeit FIG. 2a shows a single heat sink 140, the LED filament 110 may alternatively comprise two heat sinks on either side of the carrier 130. For example, the two heat sinks may be the same (or similar), or alternatively, be different, with respect to one or more properties.

[0043] FIG. 2b schematically shows a heat sink 140 of a LED filament 110 according to an exemplifying embodiment of the present invention and corresponds to the heat sink 140 shown in FIG. 2a. The base portion 150 of the heat sink 140 comprises a plurality of apertures 400 configured to transmit at least part of the LED filament light through the plurality of apertures 400. It should be noted that as an alternative to apertures 400, indentations and/or recesses may be provided. According to the example in FIG. 2b, the apertures 400 of the base portion 150 are rectangular and are spaced apart with regular intervals, such that the base portion 150 has the shape of a ladder. For example, the contact area of the heat sink 140 on the carrier, due to the provision of the apertures 400, may be in a range from 20% to 80% of the surface area of the carrier/heat sink 140.

[0044] The steps of the ladder-shaped base portion 150 correspond to the plurality of fins 160 of the heat sink 140 in FIG. 2a. The material of the heat sink 140 is preferably a metal or alloy with a relatively high thermal conductivity, such as copper (Cu) and/or aluminum (Al). The heat sink 140 may have a thermal conductivity of at least 200 Wm.sup.1K.sup.1, preferably >250 Wm.sup.1K.sup.1, more preferably >300 Wm.sup.1K.sup.1, and most preferably >350 Wm.sup.1K.sup.1.

[0045] Preferably, and according to an embodiment of the invention, the heat sink 140 comprises a metal foil, such as a copper foil. The thickness of the metal foil may be constant. The thickness of the metal foil may be in a range from 20 to 2000 m, preferably 50 to 1000 m, even more preferred 80 to 800 m, and most preferred 100 to 500 m. The thermal conductivity of the heat sink 140 is preferably at least 200 W/mK, more preferably more than 250 W/mK, and most preferred more than 300 W/mK. The heat sink 140 may be flexible. The heat sink 140 may further comprise a layer (not shown) comprising an electrically insulating material, whereby the layer constitutes an electrical insulation layer, and/or a reflective material, whereby the layer constitutes a reflective layer having a higher reflectivity than the base portion 150 of the heat sink 140. The reflective layer may reflect the incident light from the LED filament 110 during operation. The reflective layer may, for example, comprise a reflective coating. The reflective layer or coating may comprise any material of high reflectivity such as aluminum (Al) and/or silver (Ag) which may be evaporated on the heat sink 140. The reflective layer may be conveniently applied by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0046] In FIG. 2a, the LED filament 110 further comprises an encapsulant 170. The encapsulant 170 comprises a translucent material. Furthermore, the encapsulant 170 may comprise a light-scattering material configured to scatter light emitted from the plurality of LEDs 120 and/or a luminescent material configured to at least partly convert light emitted from the plurality of LEDs 120 into converted light. The light-scattering material may preferably have a reflectivity of >70%, more preferably >80%, and most preferably >85%.

[0047] The LED filament light may hereby comprise the LED light and/or the converted light. The luminescent material is configured to emit light under external energy excitation. For example, the luminescent material may comprise a fluorescent material. The luminescent material may comprise an inorganic phosphor, an organic phosphor and/or quantum dots/rods. The UV/blue LED light may be partially or fully absorbed by the luminescent material and converted to light of another color e.g. green, yellow, orange and/or red. The encapsulant 170 may be flexible. Furthermore, the encapsulant 170 may comprise silicone.

[0048] In FIG. 2a, the encapsulant 170 at least partially encloses the plurality of LEDs 120, the carrier 130 and the heat sink 140. For example, and as indicated in FIG. 2a, the encapsulant 170 fully encloses the plurality of LEDs 120. The encapsulant 170 partially encloses the carrier 130, as the length and/or width of the carrier 130 may be longer and/or wider than the length and/or width of the LED filament 110. Furthermore, the encapsulant 170 partially encloses the heat sink 140, as the plurality of fins 160 of the heat sink 140 protrudes the encapsulant 170 and extends from the encapsulant 170. The cross-section of the encapsulant 170 perpendicular to the axis, A, may be circular, but it will be noted that the encapsulant 170 may have substantially any other shape of its cross-section.

[0049] According to the example of the LED filament 110 of FIG. 2a, the plurality of LEDs 120 is arranged on a first (front) side 300 of the carrier 130, and one (single) heat sink 140 is arranged on a second (back) side 310 of the carrier 130, wherein the second side 310 of the carrier 130 is arranged opposite the first side 300 of the carrier 130. According to a non-showed example of the LED filament 110, the plurality of LEDs 120 and one (single) heat sink 140 may be arranged on the first side 300 of the carrier 130.

[0050] By the LED filament 110 in FIG. 2a, heat may be conveniently and efficiently dissipated from the LED filament 110 during operation, whilst minimizing any obstruction of the light emitted from the LED filament 110. Hence, the LED filament 110 may provide the combination of a desired light distribution from the LED filament 110 during operation, while at the same time optimizing the thermal management of the LED filament 110 via the heat sink 150.

[0051] FIG. 2c shows an alternative embodiment of the LED filament 110 shown in FIG. 2a. As many features of the LED filament 110 in FIG. 2c are similar or the same as of the LED filament 110 in FIG. 2a, some references have been omitted and it is further referred to FIG. 2a and the associated caption for an increased understanding of the LED filament 110. In FIG. 2c, the encapsulant 170 fully encloses the plurality of LEDs. The encapsulant 170 partially encloses the carrier, as the length and/or width of the carrier may be longer and/or wider than the length and/or width of the LED filament 110. Furthermore, the encapsulant 170 completely encloses the heat sink 140, including the plurality of fins 160 of the heat sink 140.

[0052] FIG. 2d shows yet another alternative embodiment of the LED filament 110 shown in FIG. 2a and FIG. 2c. As many features of the LED filament 110 in FIG. 2d are similar or the same as of the LED filament 110 in FIG. 2a, some references have been omitted and it is further referred to FIG. 2a and the associated caption for an increased understanding of the LED filament 110. In FIG. 2d, the encapsulant 170 fully encloses the plurality of LEDs. The encapsulant 170 partially encloses the carrier, as the length and/or width of the carrier may be longer and/or wider than the length and/or width of the LED filament 110. Furthermore, the length of the plurality of fins 160 of the heat sink 140 correspond to the radius of the encapsulant 170, such that the edges of the plurality of fins 160 of the heat sink 140 are arranged flush with the edge of the encapsulant 170.

[0053] It should be noted that FIGS. 2a-d show exemplifying embodiments of LED filament(s) 110, and that the shape and/or number of LED filament(s) may differ from that/those shown. For example, the LED filament(s) 100 may have a spiral, meander, coil and/or helix shape.

[0054] FIG. 3a-3c schematically show a provision of a heat sink 140 of a LED filament according to an exemplifying embodiment of the present invention. In FIG. 3a, the material and form of the heat sink 140 is provided from a metal foil, preferably a copper foil, which comprises (or alternatively, is provided with in a subsequent manufacturing step) equidistantly arranged apertures. As schematically shown in FIG. 3b, the heat sink 140 in form of the metal (copper) foil exemplified in FIG. 3a comprises perforated lines 190 provided equidistantly from the apertures 400. From a folding operation of the heat sink 140 at the perforated lines 190, a plurality of folds 200, e.g. N folds 200, wherein N is an integer, of the base portion 150 may be constructed for the heat sink 140, as indicated schematically in FIG. 3c. The folds 200 may hereby constitute the plurality of fins 160 of the base portion 150 of the heat sink 140 of the LED filament 110 as indicated in FIG. 2a. Preferably, N5, i.e. at least 5 folds 200, more preferred N10, i.e. at least 10 folds 200, and most preferred N15, i.e. at least 15 folds 200. At least one LED may be arranged between adjacent (neighboring) folds 200. The height of the folds 200 may be in a range from 1 to 10 mm, more preferably in a range from 2 to 8 mm, and most preferred in a range from 3 to 5 mm. The distance between neighboring folds 200 may be in a range from 0.5 to 10 mm, preferably 1 to 8 mm, even more preferred 2 to 6 mm, and most preferably 3 to 5 mm. The pitch (distance) between neighboring folds may be constant.

[0055] FIG. 4 schematically shows a LED lighting device 500 according to an embodiment of the present invention. The LED lighting device 500, which may constitute a lamp or a luminaire, comprises one or more LED filaments 110 according to any one of the previously described embodiments. The LED lighting device 500 further comprises a cover 510, which is exemplified as being bulb-shaped. The cover 510 may comprise an at least partially light transmissive (e.g. transparent) material and at least partially encloses the LED filament 110. The LED lighting device 500 further comprises an electrical connection 520 connected to the LED filament 110 for a supply of power to the plurality of LEDs of the LED filament 110.

[0056] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, one or more of the LED filament(s) 110, the heat sink 140, the encapsulant 170, etc., may have different shapes, dimensions and/or sizes than those depicted/described.