Patent Application
20150292724
This application claims priority to Italian Patent Application Serial No. T02014A000317, which was filed Apr. 15, 2014, and is incorporated herein by reference in its entirety.
Various embodiments may relate to lenses for lighting devices.
Various embodiments may refer to lighting devices making use, as light radiation sources, of solid-state sources such as LED sources.
Lighting devices, such as for example LED modules for outdoor use, may meet requirements such as:
high luminous flux (e.g. >10,000 lm);
Meeting such requirements may be a challenge.
In order to achieve a high optical efficiency it is possible to use optics, e.g. lenses.
On the Printed Board Assembly (PBA) side it is possible to resort to various implementations which, while satisfying some of the previously outlined needs, on the other hand may jeopardize other necessary features.
For example, a first solution consists in the use of a distributed array of light radiation sources, such as for instance high power LEDs with ceramic package (AlN or Al2O3), soldered on an Insulated Metal Substrate (IMS) board. The unit is then assembled on a heatsink (or a thermally dissipative housing, such as a metal, e.g. aluminium, housing) via a thermally-conductive glue or screws.
This solution has some limits, for example the reduced reliability of the solder joints due to the possible high Coefficient of Thermal Expansion (CTE) mismatch between the ceramic package of the light radiation source (e.g. the LED source) and the base metal (e.g. aluminium) of the board.
Another limit of such a solution is the need to reach a trade-off between the dielectric electrical breakdown, that affects the electrical insulation, and the thermal resistance. Actually, IMS boards with low thermal resistance have a rather low dielectric breakdown.
Another PBA implementation may consist in using a distributed array of light radiation sources (e.g. power LEDs with ceramic package) soldered on a ceramic board (AlN o Al2O3). The resulting unit may afterwards be assembled on a heatsink (or a thermally dissipative housing, for example of a metal as aluminium) via a thermally conductive adhesive bonding.
Under such circumstances, the thermal resistance can be similar or even lower compared to an IMS board, while the dielectric insulation may not be a critical issue, because it may be higher than 20 kV/mm with a film thickness higher than 0.3 mm.
Moreover, this implementation may show a higher reliability of solder joints, because it is possible to drastically reduce the CTE mismatch between the package of the light radiation source and the board.
However, such a solution cannot be used for a distributed LED array with a high number of LEDs, and/or in case of a large LED-to-LED pitch, because of the limited board area that may be achieved and because of the rather high cost (more than 400 /m2).
Another PBA implementation may consist in using Chip-on-Board (CoB) components manufactured on an IMS or ceramic substrate. The CoBs may be assembled on a heatsink (or a thermally dissipative housing, e.g. made of a metal such as aluminium) via a thermally-conductive glue or screws.
In the case of IMS-based CoBs, the dielectric insulation can be managed more easily with respect to packaged LEDs soldered on IMS boards. The possibility to omit a package in CoB components may lead to a reduced thermal resistance in comparison with LEDs inserted into a package and soldered on IMS boards.
As a consequence, with CoB components it is possible to use a dielectric with a higher dielectric breakdown but with a thermal conductivity which is at least slightly lower.
In the case of ceramic-based CoBs, ceramics with low thermal conductivity (for example Al2O3) may be used, because of the absence of the LED package.
Moreover, the dielectric breakdown may not constitute a significant issue, for the same reasons described for the ceramic boards.
Besides, the reliability of solder joints is not an issue, regardless of the board type employed, because the solder joints are no longer present.
The CoB solution is also attractive for cost reasons. Indeed, in some implementations it is possible to achieve up to 35% cost saving with respect to the PBA solutions using packaged LEDs soldered on an IMS board.
However, CoB solutions may have some constraints.
For example, a first constraint may be linked to the use of big lenses, which are not easy to manufacture; this may require a trade-off among the size of the optical lenses, the size of the CoBs and the costs.
Another constraint regards the interconnection between different CoBs. Such interconnections can be produced by manually soldering wires extending from a CoB to another CoB; however, there is a risk that such action may affect the dielectric breakdown features in IMS-based CoBs, leading to a possible reduction of electrical insulation.
Another possibility consists in using an additional board (for example a FR4 single layer board) as power bus line, employing connectors for the interconnection with the several CoBs; however, the use of several connectors may generate additional costs, and give rise to solutions which are not competitive in terms of cost.
In various embodiments, said object may be achieved thanks to a lens having the features specifically set forth in the claims that follow.
Various embodiments may also refer to a corresponding lighting device, as well as to a corresponding method.
Various embodiments may envisage a way to bring about the electrical interconnection between electrically powered light radiation sources (for example CoB elements or dense LED clusters mounted on small boards) and/or towards any other system which employs optical lenses.
In various embodiments, electrically conductive (e.g. copper) interconnection lines may be embedded in the optical lenses (for example made of plastics) by using processes such as co-moulding, plasma deposition or Laser Direct Structuring (LDS).
In various embodiments, by using co-moulding or plasma deposition it is possible to use standard polymer-based lenses, for example of polymethylmetacrylate (PMMA).
In various embodiments, by using an LSD process, it is possible to use plastic materials compounded with a catalyst.
In various embodiments, an optical lens with conductive, e.g. copper, lines may have such a shape as to envelope or surround a corresponding light radiation source (for example a CoB element) which is fixed by screws or glue on a heatsink or a thermally dissipative housing. This is done while ensuring a correct positioning between the light radiation source and the lens and, optionally, with the possibility to accommodate a plug-in connector, for example with sliding contacts.
In various embodiments, the electrical connection between the optical lenses and the light radiation sources (e.g. CoBs) may be obtained with an electrically conductive adhesive applied between the electrically conductive pads (e.g. copper pads) of both objects, or using the spring contacts commonly employed in optical lenses.
Various embodiments may lead to obtaining one or more following advantages:
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 invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:
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 “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the possible 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 headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
The Figures exemplify one or various embodiments of lenses 10 adapted to be used together with electrically powered light radiation sources, such as solid-state light radiation sources, e.g. LED sources.
In various embodiments, lens 10 may include a body of a material which is transparent to light radiation in the visible range. Transparent polymers such as, for example, polymethylmetacrylate (PMMA) or plastic materials compounded with a catalyst are examples of such a material.
In various embodiments, lens 10 may be produced via one of the technological processes which have already been mentioned in the introduction of the present description.
In various embodiments, the lens or each lens 10 may include a peripheral portion 10a which surrounds a portion 10b which constitutes the proper optical part of lens 10.
In various embodiments, portion 10b may have a general lenticular shape, e.g. a convex shape.
In various embodiments, peripheral portion 10a may have a polygonal external shape (e.g. a square shape in the presently shown examples) which may enable mounting several lenses 10 in an array (e.g. a matrix).
In ovarious embodiments, a lens 10 may be provided with electrically conductive lines 12, e.g. of a metal material such as copper, which are embedded in lens 10 by resorting e.g. to one of the previously mentioned technologies, i.e. by using such processes as co-moulding, plasma deposition or Laser Direct Structuring (LDS).
For example, conductive lines 12 may be respectively positive and negative supply lines for one or more electrically powered light radiation sources (e.g. LED sources) 14, to which lens 10 can be coupled according to arrangements which will be better detailed in the following.
In various embodiments, electrically conductive lines 12 may have contact terminal parts 12, 12b emerging at the lens 10 surface.
In various embodiments as exemplified herein, one or more terminals 12a may face laterally from lens 10, e.g. they may be arranged along one of the sides of peripheral portion 10a, if it is present, so as to accommodate plug-in sliding contacts of power supply lines (which are not visible in the drawings).
In various embodiments, lines 12 embedded in lens 10 may extend on the rear side of lens 10 itself, i.e. the opposite side to the front side, through which light radiation is propagated outside.
In various embodiments, one or more terminal parts 12b may therefore enable an electrical contact with electrical supply pads of the light radiation sources 14.
In various embodiments the sources consist in electrically powered light radiation sources, such as LEDs implementing e.g. the CoB technology.
In various embodiments exemplified in
The example of
Of course, both the shape of lens 10 and the general shape of the array formed by putting several lenses 10 together, and the arrangement of lenses 10 in such an array may be chosen at will.
In various embodiments, support 16 may include a heat sink (e.g. with fins) or a thermically conductive housing, such as a metal housing.
In various embodiments, light radiation source(s) 14 may be mounted on substrate 16 e.g. via screws 18 or an electrically conductive adhesive.
On the conductive pads of power sources 14 there may be arranged an electrically conductive material, for example an electrically conductive adhesive.
As it will be better understood from the sequence of
The electrical connection between electrically conductive lines 12 (ends 12b in the drawings) and the conductive pads of sources 14 may be finished by curing the previously mentioned electrically conductive adhesive.
One or more electrical connectors 20 may be plugged in by sliding, in order to contact the ends 12a of electrically conductive lines 12.
In this respect, it will be appreciated that parts or elements identical or similar to parts or elements already described with reference to
Of course, parts or elements denoted with the same reference in different Figures need not necessarily be implemented in the same way in various possible embodiments.
Moreover, one or more features exemplified herein while referring, for example, to
In various embodiments, such an integration may be implemented as a “composite” lens including a plurality of lenticular portions 10b (i.e. proper “lenses”) which are interconnected, for example in a 2×2 matrix pattern, through their respective peripheral portions 10a.
Referring to the embodiments exemplified in
In various embodiments as exemplified in
Also in the embodiments exemplified in
In this way, in various embodiments it is possible to achieve a series electrical connection of light radiation sources 14. Taking into account the fact that the arrangement of the electrically conductive lines 12 may be chosen at will, in various embodiments the connection of light radiation sources 14 may be, totally or partially, a parallel connection, according to the application requirements.
In various embodiments as exemplified in
The composite or multiple lens 10 may be applied on top of the light radiation sources 14, while achieving the desired alignment among the optical portions 10b and the light radiation sources 14.
Then the adhesive or soldering mass applied on the terminals 12b is cured, and optionally the electrical connector(s) 20 are plugged in according to the previously described procedure.
In this case, too, peripheral portions 10a of lens 10 may surround the proper optical portions 10b, each portion 10a forming a sort of frame adapted to surround a respective light radiation source 14 therein, protecting it from the outer environment.
Such a function is further shown in the examples of
As previously stated, the solution presently exemplified with reference to
In the same way,
In various embodiments, lens 10 may be provided with openings 24 (e.g. in the form of slots) for the passage of mounting screws 26.
In this case, as exemplified by the sequence of
In various embodiments, the thusly exerted pressure may allow, also thanks to the possible presence of gasket 22, to obtain a certain degree of protection, for example of IP level.
The pressure of lens 20 against the surface of support 16, for example via screws 26, may lead the spring contact terminals 12b to bring about a firm pressure contact with the pads of the light radiation sources 14.
In various embodiments, this solution (which is applicable to the embodiments exemplified in
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| TO2014A000317 | Apr 2014 | IT | national |
