EP2590480A1

EP2590480A1 - Optimized circuit board support for power LEDs

Info

Publication number: EP2590480A1
Application number: EP12189284.8A
Authority: EP
Inventors: Dario Zaccardini
Original assignee: Schneider Electric Industrie Italia SpA
Current assignee: Schneider Electric Industrie Italia SpA
Priority date: 2011-11-07
Filing date: 2012-10-19
Publication date: 2013-05-08
Also published as: ITBO20110630A1

Abstract

An optimized support (1) for power LEDs (2) which are provided with respective contact terminals (3), which comprises a layer of solid insulating material adapted to accommodate bands made of conductive material (5) which are connected to the respective contact terminals (3) of at least one component selected from LEDs (2) and active and passive electrical and electronic devices.

The bands (5) made of conductive material comprise additional incremental stratifications (6) to increase the surface for the dissipation of heat along them and to reduce their electrical and thermal resistance.

Description

The present invention relates to an optimized support for power LEDs.
In electronics, a light emitting diode or LED is an optoelectronic device that uses the optical properties of some semiconductor materials to emit photons through the phenomenon of spontaneous emission i.e. based on the recombination of electron-hole pairs.
Power LEDs are components which, following a generally higher absorption of electricity than that of standard LEDs (even higher than by an order of magnitude), are capable of generating a light beam of high intensity, and are thus adapted to illuminating contained environments and/or areas.
Generally power LEDs are mounted on terminal boards for electronic circuits of the type known as PCB (Printed Circuit Board).
In such case, depending on the power, it may be necessary to dissipate the heat generated by the LEDs and by the junction of their connection terminals to the terminal board, by making use of dedicated components like dissipators and/or PCBs with an inner core of metal, such as for example MCPCBs (Metal Core Printed Circuit Boards).
Users of LEDs make use of solutions that are easy to implement in order to ensure a correct and efficient dissipation of the heat, for example by adopting dissipators or by oversizing the heat management system.
Purchasing such components or such architectures of the terminal board, in order to ensure a sufficient dissipation of heat, although technologically straightforward and thus easy to implement, results in a considerable increase in the overall cost of the finished product.
Moreover, management of a high number of components also results in an increase in the costs of managing storage systems and the stocks of semi-finished products, thus becoming potentially not very attractive for the producer.
The aim of the present invention is to solve the above-mentioned drawbacks, by providing an optimized support for power LEDs which is adapted to dissipate the heat generated by the LEDs.
Within this aim, an object of the invention is to provide an optimized support for power LEDs which is simple and very low-cost.
Another object of the invention is to provide an optimized support for power LEDs which is constituted by a minimal number of components.
Another object of the present invention is to provide an optimized support for power LEDs which is low-cost, easily and practically implemented and safe to use.
This aim and these objects and others which will become more apparent hereinafter, are achieved by an optimized support for power LEDs which are provided with respective contact terminals, which comprises a layer of solid insulating material adapted to accommodate bands made of conductive material which are connected to the respective contact terminals of at least one component selected from among LEDs and active and passive electrical and electronic devices, characterized in that said bands made of conductive material comprise additional incremental stratifications to increase the surface for the dissipation of heat along them and to reduce their electrical and thermal resistance.
Further characteristics and advantages of the invention will become more apparent from the description of a preferred, but not exclusive, embodiment of the optimized support for power LEDs according to the invention, which is illustrated by way of non-limiting example in the accompanying drawings wherein:

Figure 1 is a schematic perspective view of a support according to the invention, on which a plurality of power LEDs are installed;
Figure 2 is a schematic cross-sectional view of a support according to the invention, on which a power LED is installed.

With particular reference to the figures, the reference numeral 1 generally designates an optimized support for power LEDs 2.
A double-sided rigid printed circuit is generally made up of an insulating substrate that is solid, flat and of constant thickness. These materials are known as "base materials" and are essentially distinguished by their different dielectric rigidity, and their capacity to withstand high temperatures and/or thermal stresses.
A layer of copper laminate with a constant preset thickness is applied on both of the external faces of the substrate, with a strong adhesive composed of glass cloth impregnated with resin. The plate 4 thus obtained can be perforated in order to allow electrical connections through metalized holes thus providing the electrical connection between the upper and lower planes of the plate 4. As SMD components, the terminals 3 of the LEDs 2 are directly soldered to the upper plane of the plate 4. For obtaining the set of connection bands 5 (known as "traces" in the technical jargon) alone, the excess copper is selectively chemically removed from the copper-covered plane.
The electrical connection between the upper layer of copper and the lower layer of copper occurs by way of metalization of all the holes that were made previously, i.e. both the holes where subsequently the various components will be inserted, and also special holes (called "vias") made solely for the purpose of connecting the upper layer to the lower layer, are metalized.
The optimized support 1 for power LEDs 2 thus comprises a layer of solid insulating material adapted to accommodate bands 5 made of conductive material which are connected to the respective contact terminals 3 of at least one component selected from LEDs 2 and active and passive electrical and electronic devices.
The bands made of conductive material 5 of the support 1 according to the invention comprise additional incremental stratifications 6 to increase the surface for the dissipation of heat along them and to reduce their electrical resistance.
The additional incremental stratifications 6 can have, according to an embodiment of particular effectiveness, dimensions which are proportional to the amount of heat generated by the LEDs and by the devices.
When the LED 3 is switched on, the junction of the LED 3 generates heat and, given that the area of the semiconductor that generates light (and heat) for an LED 3 rated at 1W is generally approximately 1-2mm², the area/power ratio is very low and the heat must be dissipated in order to prevent the LED from burning out due to exceeding the maximum temperature of the junction, or in order to prevent shortening of the lifetime of the LED seeing that it is inversely proportional to the operating temperature of the junction.
By increasing the mass of the dissipating material (copper) of the plate 4 proportionally to the quantity of heat generated by the components (LEDs 2) which are connected to it, the thermal resistance between the soldering point of the LED 3 and the environment is reduced, thus significantly reducing the operating temperature of the junction (thanks to the quantity of heat removed by the stratification 6).
The additional incremental stratifications 6, according to a possible practical application that is particularly advantageous in applicative terms, can have an outer surface that is not smooth so as to increase the surface exposed to the environment and therefore the surface of the stratifications through which heat is dissipated.
If the outer surface is irregular, affected by a plurality of notches, cells or protrusions of various shapes, naturally the stratification 6 will be adapted to transfer the heat to the outside environment more rapidly and with greater efficiency.
It is convenient to note that, in the area where the contact terminal 3 of the LED 2 is fixed to the band 5 and to the corresponding additional incremental stratification 6, the volume of conducting material associated with each terminal 3 is greater than the volume present in a printed circuit of the standard type.
This determines a consequent increase in the heat conduction of such junction and therefore in the transfer of heat from the LED 3 to the band 5 and to the corresponding stratification 6.
It should be noted in particular that the additional incremental stratifications 6 can conveniently be arranged on the bands 5 only in the areas that are contiguous to the connecting points of the contact terminals 3 of the LEDs 2 and of the devices with the corresponding band 5.
In this manner it will also be possible to make use of the presence of additional stratifications 5 on metalized holes of the plate 4 which are not electrically connected to the respective terminal 3 but are only proximate to it. In fact, through conduction, the heat will also reach such holes which are proximate to the LED 2 and, by way of the stratification 6 present on them, this heat can effectively be dissipated to the outside environment, thus keeping the temperature of the component within the rated range specified by the manufacturer.
Advantageously, the present invention solves the previously mentioned drawbacks, by providing an optimized support 1 for power LEDs 2 which is adapted to dissipate the heat generated by the LEDs 2. Such dissipation of heat will conveniently be designed so that the stratifications are adapted to remove the right amount of heat thus preventing oversizing which could result in excessive increases in weight and/or cost for the support 1.
Conveniently the present invention describes an optimized support 1 for power LEDs 2 which is simple and very low-cost. This is possible thanks to the use of inexpensive materials which are applied directly on the plates 4 that are normally used (PCBs).
Effectively, the optimized support 1 for power LEDs 2 is constituted by a minimal number of components. This ensures a greater effectiveness of operation and a definite reduction in costs with respect to conventional solutions for removal of the heat generated by the LEDs 3.
The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.
In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be interchanged with other, different characteristics, existing in other embodiments.
In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.
The disclosures in Italian Patent Application No. BO2011A000630 from which this application claims priority are incorporated herein by reference.
Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

An optimized support for power LEDs (2) which are provided with respective contact terminals (3), which comprises a layer of solid insulating material adapted to accommodate bands made of conductive material (5) which are connected to the respective contact terminals (3) of at least one component chosen from LEDs (2) and active and passive electrical and electronic devices, characterized in that said bands (5) made of conductive material comprise additional incremental stratifications (6) to increase the surface for the dissipation of heat along them and to reduce their electrical and thermal resistance.
The support according to claim 1, characterized in that said additional incremental stratifications (6) have dimensions which are proportional to the amount of heat generated by the LEDs (2) and by the devices.
The support according to claim 1, characterized in that said additional incremental stratifications (6) have an outer surface that is not smooth so as to increase the surface exposed to the environment and therefore the surface of said stratifications through which heat is dissipated.
The support according to claim 1, characterized in that at the area where the contact terminal (3) of the LED (2) is fixed to the band (5) and to the corresponding additional incremental stratification (6), the volume of conducting material associated with each terminal (3) is greater than the volume present in a printed circuit of the standard type, with a consequent increase in the heat conduction of said junction and therefore in the transfer of heat from the LED (2) to the band (5) and to the corresponding stratification (6).
The support according to claim 1, characterized in that said additional incremental stratifications (6) are arranged on said bands (5) at the areas that are contiguous to the connecting points of the contact terminals (3) of said LEDs (2) and said devices with the respective band (5).