Abstract:
A lighting device may include a mounting board with first and second opposed faces and vias extending therethrough, one or more light radiation sources mounted on the first face of the mounting board, drive circuitry for the light radiation source mounted on the second face of the mounting board, with electrically conductive lines between the light radiation source and the drive circuitry passing through said vias, a vat-like holder housing the mounting board with the light radiation source and the drive circuitry mounted thereon. The holder has cavities for receiving therein the drive circuitry with the first face of the mounting board and the light radiation source mounted thereon facing outwardly of the holder. Over the first face of the mounting board at least one sealing layer is applied, which ensures an IP grade protection of device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Italian Patent Application Serial No. TO2013A000728, which was filed Sep. 9, 2013, and is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     Various embodiments relate generally to lighting devices. 
     Various embodiments may refer to Solid State Lighting (SSL) devices, such as lighting devices which make use of LED sources. 
     BACKGROUND 
     Various implementations of solid state lighting modules are known (for example flexible LED modules) in which the electrical and electronic components (light radiation source(s), resistors, capacitors, LED drivers etc.) are mounted on a single side of a board (e.g. similar to a Printed Circuit Board, PCB). In such implementations, all components therefore are located on the side which is visible to the end user, with possible disadvantages of various kinds. 
     For example, there may be limitations in the choice of the electrical and electronic components: if the number of such components is high, the radiation pattern may be uneven, with a consequent reduction of the device efficiency. 
     The electrical/electronic components are usually black or dark, and this colour may eventually produce visible black spots when the lighting module is off. 
     On the one side, it might be possible to ask suppliers to produce components with a white or other light colour package; this however might cause an increase in costs. 
     The drawback might also be limited by covering the dark components with a coating, for example a silicone coating, of a white colour, without covering the light radiation sources, also taking into account the fact that the sealing from the outer environment (IP protection) may be achieved with a two-step process: 
     a first step, in which the board surface is covered by e.g. a silicone layer, of a white colour, so as to cover the dark components, without covering the Light Emitting Surface(s) (LES); 
     a second step, in which the whole surface of the board (including what has already been covered with the white layer) is coated with a further transparent, i.e. light-permeable, layer (e.g. a silicone layer), so as to ensure an efficient light transmission while achieving an IP protection (Ingress Protection Rating) as well. 
     In order to simplify the process, and specifically the first step thereof, the light radiation sources (which must remain exposed) and the drive circuitry (which on the contrary must be covered and masked by a white layer) must not be present in too high a number. 
     Moreover, in various implementations, such a process may impose limitations in the choice of sources, e.g. because of the difficulty of using LEDs with high performance and reliability and low cost. 
     More generally speaking, another constraint may come from the fact that the LED-to-LED pitch is influenced by the space needed to mount the other electrical and electronic components. 
     SUMMARY 
     Various embodiments aim at overcoming the previously outlined drawbacks. 
     Various embodiments may offer one or several of the following advantages: 
     only the light radiation sources (e.g. the LEDs) are visible from the outside of the final product; 
     a wide range of light radiation sources (e.g. LEDs) may be used, with advantages in terms of cost; 
     the silicone deposition process is simpler and more rapid, with the possibility of achieving productivity increases by about 50%, 
     less silicone may be used for the module protection, thereby reducing the cost of raw materials; 
     it is possible to achieve modules with reduced thickness and/or reduced LED-to-LED pitch, 
     in comparison with current implementations, a higher number of electronic components (twice as many) may be mounted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the disclosure. In the following description, various embodiments of the disclosure are described with reference to the following drawings, in which: 
         FIGS. 1 to 4  show subsequent steps of a method to achieve devices according to various embodiments, and 
         FIGS. 5 and 6  show variations of embodiments. 
     
    
    
     DESCRIPTION 
     In the following description, numerous specific details are given to provide a thorough understanding of various exemplary embodiments. One or more embodiments may be practiced without one or several specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the embodiments. Reference throughout this specification to “one or more embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. 
     The sequence of  FIGS. 1 to 4  shows subsequent steps of a method for obtaining, according to various embodiments, a lighting device  10  which makes use, as a light radiation source  12 , of a solid state source, such as a LED source (either single or plural: for simplicity, the figures refer to a single source  12 ). 
     In various embodiments, the source  12  may be mounted on a board  14 , substantially similar to a printed circuit board. 
     In various embodiments, the board  14  may be made of an electrically insulating material, e.g. (optionally flexible) polyimide. 
     In various embodiments, as exemplified in the Figures, the board  14  may have two opposite faces, on which there are formed, according to known criteria, conductive lines  16  (of an electrically conductive material, e.g. copper) that are adapted to define transmission paths for electrical (supply and/or control) signals which connect the source  12  to drive circuits, which are denoted on the whole by  18 . 
     In various embodiments, the source  12  and the components  18  may be connected (optionally also mechanically) to the lines  16  by soldering and/or via an electrically conductive adhesive, as schematically shown at  20  in  FIG. 2  and the following Figures. 
     The nature of the electrical/electronic components  18 , as well as the topology of the conductive lines  16 , are not of particular relevance to various embodiments. The same may be true, for example and with no limitations, for the masks which define the paths of the conductive lines  16 . 
     In various embodiments, through the body of board  14  (the side edges whereof are denoted with  22 ) there may extend lines or connection “vias”  24  for the electrical connection between the source  12 , mounted on the “front” face of the board  14 , and the drive circuits  18 , which on the contrary are mounted on the “back” face of board  14 . In this way, on the front face of the board  14 , only the light radiation source(s)  12  is/are visible from the outside, while the drive circuits  18 , mounted on the opposite face, i.e. on the back face, are hidden from the outside. 
     In various embodiments a lighting module or device  10  is implemented that has an IP protection grade, and which may be flexible or “flex”, thanks to the flexibility of the board  14 . 
     In various embodiments, the components  18  may be mounted on the back face of the board  20 , for example via standard methods such as SMD processes and/or by using electrically conductive adhesives or soldering masses, possibly in combination (for example soldered/welded layers and conductive adhesive layers coated in sequence). 
     In various embodiments, it is possible to use a generally vat-like holder  28 , e.g. including silicone-based, and therefore flexible material of a generally white colour. Such a holder may be produced e.g. by extrusion or molding. 
     In various embodiments, the holder  28  can be provided, e.g. in the bottom wall, with cavities  30  adapted to accommodate the circuits  18  mounted on the back face of board  26 . 
     In various embodiments, this enables to match the shape of the holder  28  and the shape of the “bare” module (i.e. the board  14  with the source(s)  12  and components  18  mounted on the opposite faces thereof). 
     In various embodiments, this bare module may be inserted into the holder  28 , as schematically shown in  FIG. 3 , and then the bare module may be glued to holder  28 . 
     In various embodiments, the holder  28  may have a general vat shape with a bottom wall (where the cavities  30  may be arranged) and peripheral walls  32  adapted to surround the basic module (board  14 , light radiation source(s)  12  and components  18 ) in conditions wherein the side edges  22  of the board  14  contact the side walls  32  of the holder  28 , or at least are adjacent to them. 
     The figure exemplifies various embodiments wherein it is possible to achieve a sealing of the circuit  10 , providing it with a protection grade (for example IP) against the penetration of external agents, without having to perform two subsequent steps of applying, first of all, a white sealing mass (e.g. silicone-based), and then a transparent (i.e. light-permeable) mass, according to the criteria recalled in the introduction of the present application. 
     In  FIG. 4  there is shown the possibility, in various embodiments, of achieving a sealing from the environment by applying a single transparent (i.e. light-permeable) sealing mass  34 , thereby implementing one single step and reducing the related costs. 
     As schematically depicted in  FIG. 4 , in various embodiments the sealing mass or layer  34  may cover the whole front face of board  13  (including the light radiation source(s); being transparent, the layer  34  does not block light radiation), while sealingly connecting to the side walls  32  of the holder  28 , i.e. while sealing the peripheral area where side edges  22  of the board  14  face (e.g. contact) the side walls  32  of the holder  28 . In such embodiments, the sealing mass  34  may therefore extend beyond the contours of the soldering mask, i.e. to areas external to the paths of the lines  16 . 
     Instead of a single transparent sealing mass, such as mass  34 , various embodiments, as exemplified in  FIGS. 5 and 6 , may make use of two sealing masses or layers: 
     the former, denoted by  36 , being of a white colour, and 
     the latter, denoted by  38 , being transparent (and therefore light-permeable). 
     This allows to meet further requirements than in current implementations. 
     For example,  FIG. 5  shows the possibility to apply a first thin sealing mass or layer  36  of a white colour, which is adapted to cover the front face of the board  26  while leaving the light radiation source(s)  12  exposed. 
     In various embodiments, on the front face of the board  14  there may be only provided the light radiation source(s)  12  (the drive circuits  18  being mounted on the back face); this simplifies the application of a layer  36  of reduced thickness, which leaves the source(s)  12  exposed while extending to cover the front face of the board  14  (and the conductive lines  16  provided thereon) with a substantially planar extension profile, which does not have to “wrap” any circuit component in order to mask it. 
     The possible use of a very thin layer  36  opens up a wide range of choice of the light radiation source(s)  12 , enabling therefore the use of low-cost LEDs without taking into account factors such as the package size. 
       FIG. 6  exemplifies that, in various embodiments, on the layer  36  it is then possible to apply a subsequent transparent sealing layer  38 , of a light-permeable material, which therefore, in the same way as the layer  34  described with reference to  FIG. 4 , may extend to cover the source(s)  12  as well without blocking the light emission by the device  10 . 
     As in the case of the layer  34 , in various embodiments the layer  36  and/or the layer  38  may connect sealingly with the side walls  32  of the holder  28 , while sealing the peripheral area where the side edges  22  of the board  14  face (e.g. contact) the side walls  32  of the holder  28 . 
     As a consequence, irrespective of the solution chosen, whether: 
     of a single transparent layer  34  which covers the source(s)  12  as well ( FIG. 4 ), or 
     of a first white layer  36  which leaves the source(s)  12  exposed ( FIG. 5 ) and of a second transparent layer  38  which covers the source(s)  12  as well ( FIG. 6 ), 
     in various embodiments at least one sealing layer  34  or  38  is present which is made of light-permeable material, at least at the source(s). 
     Whatever the solution adopted, the application criteria of sealing layers/masses  34 ,  36 ,  38  correspond to solutions known per se, so that they do not require a detailed description herein. 
     While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.