Brevet FR3103059A1 — publié le 20210514

The present disclosure relates to light emitting diodes and more specifically discloses an encapsulating layer (10) mounted on an LED array (20). The encapsulating layer (10) covering the LED array (20) is moulded separately and is mounted on a PCB (30) with adhesive means. The encapsulating layer has blisters contoured to accommodate LEDs underneath. The encapsulating layer of the present disclosure is one that enhances optical performance of the LED array by eliminating air bubble formation, is safe to operate hazard prone areas and one which eliminates emission of volatile organic compounds as use of primers and curing of the encapsulant fluid is eliminated. Figure de l’abrégé : Fig. 3 MOTEUR A DEL The present disclosure relates to Light Emitting Diodes (LEDs) and more particularly to encapsulated LED arrays. The background information herein below relates to the present disclosure but is not necessarily prior art. An encapsulating layer is generally provided on an LED array of an LED engine to eliminate possibility of fire hazard due to spark generated by the LED array. Presently, the method of encapsulating Light Emitting Diode (LEDs) arrays involves coating or potting optical grade fluid on the LED directly, followed by curing of the fluid. However, this results in formation of air bubbles within the coat or encapsulant which reduce the optical performance of the coating, as well as decreases reliability of the encapsulated LEDs. Moreover, the presence of air bubbles is not permitted by the product standards. The conventional coating process requires significant amount of time in producing encapsulated LEDs in order to avoid formation of air bubbles. The coating process also requires use of primers to achieve adhesion. The primers release flammable volatile organic compounds (VOCs) during the curing process, which in turn requires expensive equipment to prevent fire hazard. There is, therefore, felt a need to overcome the aforementioned problems related to encapsulating layers for LED arrays in an LED engine. OBJECTS Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows: An object of the present disclosure is to provide an LED engine with an encapsulated LED array wherein the encapsulating layer is free from air bubbles. Another object of the present disclosure is to provide an LED engine with an encapsulated LED array which does not require use of primers and curing of the encapsulating fluid. Still another object of the present disclosure is to provide an LED engine with an encapsulated LED array that complies with the product standards in hazardous areas with Zone 1 classification. Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure. The present disclosure relates to an LED engine comprising a printed circuit board (PCB), at least one LED array mounted on the PCB and an encapsulating layer. The LEDs of the LED array are electrically connected to each other. The encapsulating layer is configured to encapsulate the LED array and the electrical connections therebetween. The encapsulating layer is fixed to the PCB with an adhesive means. The encapsulating layer comprises a plurality of blisters contoured to accommodate LEDs of the LED array underneath, and is further configured to transform the light emitted by the LED array into a desired light beam pattern. At least one planar portion is configured to encapsulate electrical connection formed on the printed circuit board. Preferably, the encapsulating layer is pre-moulded and is separate from the LED array and the PCB. The shape of the blisters is selected from the group consisting of semi-circular, circular, oval, eye-shaped, elliptical, rectangular, and square. The adhesive means is an adhesive tape with glue on both sides. In an embodiment, gaps are formed between the LED array and the encapsulating layer, wherein the gaps are filled with an encapsulating fluid. In one embodiment, retention means are provided integral to the encapsulation layer to safeguard wires of the LED array protruding from the PCB. Preferably, the blisters have optical transmittance in the range of 85% to 93%. In an embodiment, the thickness of the encapsulating layer is non-uniform. Preferably, the material used for manufacturing the encapsulating layer is silicone. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING The LED engine of the present disclosure will now be described with the help of the accompanying drawing, in which: and and and illustrate formation of air bubbles in an encapsulating layer of the prior art; illustrates a schematic top view of an LED engine, in accordance with an embodiment of the present disclosure; illustrates a partially exploded view of the LED engine of Figure 2 with the encapsulating layer removed from the PCB; illustrates details of section A-A of Figure 2; illustrates a bottom view of the encapsulating layer of Figure 3; illustrates a bottom view of another embodiment of the encapsulating layer of Figure 3; illustrates an isometric view of the power supply wires and adjoining areas of the LED engine of Figure 2; illustrates an isometric bottom view of the LED engine of Figure 2; illustrates a top view of a blister of an encapsulating layer, in accordance with another embodiment of the present disclosure; illustrates a schematic of a sectional view of a blister of Figure 8a; illustrates a polar plot of a light pattern generated by the blister of Figure 8a; illustrates a top view of a blister of an encapsulating layer, in accordance with another embodiment of the present disclosure; illustrates a sectional view of a blister of Figure 8a along section B-B; illustrates a sectional view of a blister of Figure 8a along section C-C; and illustrates a polar plot of a light pattern generated by the blister of Figure 9a. LIST OF REFERENCE NUMERALS 100 – LED engine 10 – encapsulating layer 20 – LED array 30 – printed circuit board (PCB) 40 – adhesive means 50 – blister 52 – planar portion 60 – gap 70 – channels 72 –inlet port 74 –outlet port 80 – retention means 82 – cavity for wires 85 – wires of LED array Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail. The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms “comprises”, “comprising”, “including” and “having” are open-ended transitional phrases and therefore specify the presence of stated features, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed. When an element is referred to as being “mounted on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed elements. Terms such as “inner”, “outer”, “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used in the present disclosure to describe relationships between different elements as depicted from the figures. Referring to Figures 1a-1d, an encapsulating layer of an LED engine of prior art with air bubbles is shown. Presently, the method of encapsulating Light Emitting Diode (LEDs) arrays involves coating or potting optical grade fluid on the LED directly, followed by curing of the fluid. The formation of air bubbles within the coat or encapsulant reduces the optical performance of the coating, as well as decreases reliability of the encapsulated LEDs. In addition to this, presence of air bubbles is not permitted by product standards. Referring to Figures 2-9d, the construction of an LED engine 100 in accordance with an embodiment of the present disclosure is shown. The LED engine comprises a printed circuit board (PCB) 30 and at least one LED array 20 mounted on the PCB 30. LEDs of the LED array 20 are electrically connected to each other. An encapsulating layer 10 is configured to encapsulate the LED array 20 and the electrical connections therebetween. The encapsulating layer 10 is fixed to the PCB 30 with an adhesive means 40, as shown in Figure 4. The encapsulating layer 10 of the LED engine 100 is manufactured by injection moulding separately from the LED array 20. Thus, the encapsulating layer 10 is pre-moulded and is later assembled with the LED array 20 that is mounted on a PCB 30, as shown in Figure 3. The encapsulating layer 10 is fixed to the printed circuit board 30 covering the LED array 20. The encapsulating layer 10 has blisters 50 and a planar portion 52 between the blisters 50, as shown in Figure 5. The blisters 50 are contoured to accommodate LEDs underneath. The planar portion 52 has channels formed between adjacent blisters for encapsulating the electrical connections between adjacent LEDs in the LED array 20. The encapsulating layer 10 is fixed to the PCB 30 with adhesive means 40, which is typically an adhesive tape with glue on both of its sides. Each of the blisters 50 of the encapsulating layer 10 has a shape selected from the group consisting of a semi-circle, an ellipse, a rectangle, shape of an eye, an oval and a square, which facilitates accommodation of variable shapes of LED array 20. The blisters 50 have optical transmittance in the range of 85% to 93%. The encapsulating layer 10 is typically made of a mouldable material such as silicone which allows excellent fluidity. Preferably, for manufacturing the pre-moulded encapsulating layer 10 of the present disclosure, a silicone typically requiring 1:1 mixing ratio by volume of the silicone and a catalyst, with the silicone of polydimethylsiloxane elastomer, is used. In an embodiment, silicone of grade MS 1002 is used. As shown in Figures 5a, 5b, and 6, a retention means 80 is provided integral to the encapsulation layer 10 to safeguard the wires 85 against unnecessary strain placed on them during handling. The retention means 80 is typically a cover which engulfs the connection of the wires 85 attached to the PCB 30. The retention means 80 has a cavity 82 for accommodating the wires 85 underneath. Between the retention means 80 and the wires 85, a space is formed in which a fluid can be filled to provide security to the wires 85 against unnecessary strain. The construction of the encapsulating layer 10, as described above, ensures absence of bubbles within the encapsulating layer 10, as the pre-moulded encapsulating layer 10 is simply assembled on to the LED array 20 which is mounted on the PCB 30. Thus, the LED array 20 stays insulated between the encapsulating layer 10, the adhesive means 40 and the PCB 30, as desired, to prevent damage to the LED array 20 by environmental factors such as air, water or contaminants that would hamper the optical performance of the LED array 20. The encapsulating layer 10 thus has enhanced optical performance and is reliable due to absence of air bubbles. Moreover, the encapsulating layer 10 eliminates possibility of explosion or fire in sensitive operating conditions, especially in areas of Zone 1 classification. Thus, the LED engine 100 with the encapsulating layer 10 offers compliance with the product standards. Thus, the encapsulating layer 10 reduces risk of fire hazard by eliminating use of primers which are highly volatile and inflammable, and is free from emission of volatile organic compounds. Between the lower surface of blisters 50 of the encapsulating layer and the LEDs in the array 20, gaps 60 are formed. In one embodiment (as shown in figure 4), the gaps 60 also are filled with the same or alternatively another optical material to impart strength to the encapsulating layer 10, as well as to obtain varying characteristics of the LED light pattern. Channels 70 are provided on the encapsulating layer 10 on its underside. This allows further filling the gaps 60 of the LED array 20 with the same or alternatively another encapsulating fluid as an alternative embodiment. Also provided is an inlet port 72 on the PCB 30 on one end through which the encapsulating fluid is injected, as shown in Figure 7. The encapsulating fluid then passes through the gaps 60 to finally eject through an outlet port 74 on another end of the LED array 20, once the gaps 60 are completely occupied and no more room is left. In an alternative embodiment (as shown in figure 4, the gaps 60 formed between the lower surface of the blisters 50 of the encapsulating layer 10 and the LEDs in the array 20 are maintained void. Referring to Figures 8a-8c, polar plots of the light pattern generated by a circular shaped blister 50 of the encapsulating layer 10 as shown in Figure 8a are shown in Figure 8c. Figure 8b shows a cross-sectional view of the blister 50 of Figure 8a. Referring to Figures 9a-9d, polar plots of the light pattern generated by an elliptical blister 50 of the encapsulating layer 10 as shown in Figure 8a are shown in Figure 9d. Figures 9b, 9c show cross-sectional views of the blister 50 of Figure 9a. From an industrial perspective, the construction of the LED engine 100 as disclosed in the present disclosure allows flexibility of combining encapsulating layers with different variants of beam patterns with LEDs of various power and colour, at the last minute on the final assembly line. Thus, customization of small to medium batches is possible without requiring creation of sizeable stocks in all possible variants of LED arrays. The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure. TECHNICAL ADVANCEMENTS The present disclosure described herein above has several technical advantages including, but not limited to, the realization of an LED engine with an encapsulated LED array wherein the encapsulating layer: is devoid of air bubbles; has enhanced optical performance of the LED array due to absence of air bubbles; reduces risk of fire hazard by eliminating use of primers which are highly volatile and inflammable; is free from emission of volatile organic compounds, as application of primer and curing of the encapsulant fluid is eliminated; offers compliance with the product standards in hazardous areas with Zone 1 classification; and allows last minute customization of LED arrays. The foregoing disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration. The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Any discussion of materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application. The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary. While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. An LED engine (100) comprising: - printed circuit board (PCB) (30); - at least one LED array (20) mounted on said PCB (30), wherein LEDs of said LED array (20) are electrically connected to each other; and - an encapsulating layer (10) configured to encapsulate said LED array (20) and the electrical connections therebetween, wherein said encapsulating layer (10) is fixed to said PCB (30) by an adhesive means (40). The LED engine (100) as claimed in claim 1, wherein said encapsulating layer (10) comprises: - a plurality of blisters (50) contoured to accommodate LEDs of said LED array (20) underneath, and is further configured to transform the light emitted by said LED array (20) into a desired light beam pattern; and - at least one planar portion (52) configured to encapsulate electrical connection formed on said printed circuit board (30). The LED engine (100) as claimed in claim 1, wherein said encapsulating layer (10) is pre-moulded and is separate from said LED array (20) and the PCB (30). The LED engine (100) as claimed in claim 1, wherein the shape of said blisters (50) is selected from the group consisting of semi-circular, circular, oval, eye-shaped, elliptical, rectangular, and square. The LED engine (100) as claimed in claim 1, wherein said adhesive means (40) is an adhesive tape with glue on both sides. The LED engine (100) as claimed in claim 1, wherein gaps (60) are formed between said LED array (20) and said encapsulating layer (10). The LED engine (100) as claimed in claim 6, wherein said gaps (60) are filled with an encapsulating fluid. The LED engine (100) as claimed in claim 1, wherein a retention means (80) is provided integral to the encapsulation layer (10) to safeguard wires (85) of said LED array (20) protruding from said PCB (30). The LED engine (100) as claimed in claim 1, wherein said blisters (50) have optical transmittance in the range of 85% to 93%. The LED engine (100) as claimed in claim 1, wherein the thickness of said encapsulating layer (10) is non-uniform. The LED engine (100) as claimed in claim 1, wherein the material used for manufacturing said encapsulating layer (10) is silicone.