EP2541139A2 - LED lighting module - Google Patents

Abstract

The module (10) has a printed circuit board (PCB) (30) formed with a continuous aperture (70), and an LED (40) fixed into the aperture. A cooling body (20) i.e. metal plate, comprises a surface, which runs parallel to the PCB. The LED is mounted such that light emitted from the LED passes through a part of the aperture. A housing surface of the LED partially runs between the PCB and the surface of the body. The aperture is smaller than a base surface of the LED. Distance between the PCB and the body corresponds to expansion of the LED in a light emission direction.

Description

Embodiments of the present invention relate to lighting modules, in particular using light emitting diodes (LED). In particular, they relate to LED lighting modules with simplified production and improved dissipation of the heat loss.

With the development of light emitting diodes (LED) with white light characteristics and a concomitant steady increase in performance, LEDs have in recent years become a promising alternative to traditional lighting in both the residential and commercial sectors, as well as in the public sector. Thus, for example, in the area of street lighting dominated by metal halide lamps (for example, sodium vapor lamps and mercury vapor lamps), LED technology has been increasingly used, which has developed into an advantageous alternative in terms of service life, luminous efficacy and cost aspects. In contrast to the largely developed, conventional metal vapor technology, the LED technology is characterized by continuous development, which in many aspects further significant progress can be expected. Therefore, significant market shifts have already begun.

For example, a 2009 study by the University of Pittsburgh compared street lighting with LEDs to high-pressure sodium and metal halide ( Hartley et al .: Life Cycle Assessment of Streetlight Technologies, University of Pittsburgh, July 2009 ) The result of the study was that the LED lighting already in 2009 produced a similar resource consumption over the lifetime as the other technologies, whereby the LEDs still big potential for the optimization certified. Therefore, the authors recommended in the medium term a complete switch to LEDs for street lighting. Since the study, LED technology has evolved significantly in terms of luminous efficacy and energy efficiency, so that the benefits predicted at that time are already reality.

The constant increase in luminance has at the same time relativized an aspect that once characterized LEDs as a "cold" alternative to conventional incandescent or discharge lamps. For example, standard white high-power LEDs use power losses of more than 10 watts with external dimensions (base area) of less than about 1 cm ² . Since both efficiency or power output, as well as the life are negatively affected by the increasing temperature of the semiconductor substrate, it is therefore an increasing Challenge to derive the occurring power loss quickly and reliably. Typically, to achieve sufficient illuminance several individual LEDs are combined to form a lighting module, that is in practice mounted in a matrix-like manner on a common base such as a printed circuit board. High-power LEDs usually have approximately the shape of a flat disc or a very flat cuboid. They are typically mounted and contacted like conventional electronic components on the component side of the printed circuit board. Because the glass fiber-epoxy composite of conventional circuit boards is a poor conductor of heat compared to metals such as copper or aluminum, various techniques for improving heat dissipation have been developed.

This includes, for example, a composite of a layer of printed circuit board material (PCB) with a directly underlying aluminum plate. The LEDs are applied and contacted on the PCB material, wherein the aluminum plate takes over the task of heat dissipation and the heat sink. However, these and similar solutions have several disadvantages. On the one hand, such composite printed circuit boards are more expensive than conventional printed circuit boards because of the smaller numbers and their complex structure, on the other hand, the printed circuit board material, or possibly further insulation layers, an undesirable thermal barrier between the LED and the aluminum plate.

To solve this problem, additional techniques have been introduced to improve the heat transfer. For example, metal feedthroughs through the PCB are used to provide better thermal contact between the LED back and the aluminum plate. However, these passages through the printed circuit board or related solutions increase the manufacturing complexity, the number of manufacturing steps, and the cost. In addition, such feedthroughs are typically realized only under part of the cross-sectional area of the LED housing (cf., for example: Osram Opto Semiconductors: "Thermal Management of Golden Dragon LEDs", Application Note, October 2008 ).

In view of the stated problems, it is an object of the present invention to provide an LED lighting module which avoids the disadvantages of the known solutions.

This object is achieved, at least in part, by an LED lighting module according to claim 1.

According to a first aspect, an LED lighting module is provided. The LED lighting module comprises a circuit board having first and second sides and at least one through opening, at least one light emitting diode mounted on the opening, on the first side of the board, having a light emitting face and a non-emitting face Light emitting diode is mounted with its light-emitting front to the first side of the board so that emitted light passes at least part of the opening and exits on the second side of the board, and that the back of the LED is exposed, so that the module with the not Light-emitting back of the LED can be attached to a heat sink.

Further advantages, features, aspects and details of the invention as well as preferred embodiments and particular aspects of the invention will become apparent from the claims, the description and the figures.

• Fig. 1 zeigt eine Draufsicht auf ein LED-Beleuchtungsmodul gemäß Ausführungsbeispielen.
• Fig. 2 zeigt eine Seitenansicht des LED-Beleuchtungsmoduls der Fig. 1.
• Fig. 3 zeigt eine schematische Querschnittsansicht durch eine Lampe mit LED-Beleuchtungsmodulen gemäß Ausführungsbeispielen.
• Fig. 4 zeigt eine seitliche schematische Querschnittsansicht durch eine Lampe mit LED-Beleuchtungsmodulen gemäß Ausführungsbeispielen.
• Fig. 5 zeigt eine schematische Querschnittsansicht einer Lampe mit LED-Beleuchtungsmodulen gemäß Ausführungsbeispielen.
• Fig. 6 zeigt eine Draufsicht auf ein LED-Beleuchtungsmodul gemäß weiteren Ausführungsbeispielen.
• Fig. 7 zeigt eine schematische Draufsicht auf ein LED-Beleuchtungsmodul gemäß Ausführungsbeispielen.
• Fig. 8 zeigt eine Querschnittsansicht durch ein LED-Beleuchtungsmodul gemäß Ausführungsbeispielen.
• Fig. 9 zeigt eine Querschnittsansicht durch ein LED-Beleuchtungsmodul gemäß weiteren Ausführungsbeispielen.

In addition, the invention will be explained with reference to exemplary embodiments illustrated in figures, from which further advantageous parts and modifications result. Showing:

• Fig. 1 shows a plan view of an LED lighting module according to embodiments.
• Fig. 2 shows a side view of the LED lighting module of Fig. 1 ,
• Fig. 3 shows a schematic cross-sectional view through a lamp with LED lighting modules according to embodiments.
• Fig. 4 shows a side schematic cross-sectional view through a lamp with LED lighting modules according to embodiments.
• Fig. 5 shows a schematic cross-sectional view of a lamp with LED lighting modules according to embodiments.
• Fig. 6 shows a plan view of an LED lighting module according to further embodiments.
• Fig. 7 shows a schematic plan view of an LED lighting module according to embodiments.
• Fig. 8 shows a cross-sectional view through an LED lighting module according to embodiments.
• Fig. 9 shows a cross-sectional view through an LED lighting module according to further embodiments.

The following is an example of conventional high-power LEDs, each about 1 cm long, 1 cm wide and about 2 mm high. However, this is only to be regarded as a non-limiting example, embodiments of the invention also relate to differently shaped light-emitting diodes with other dimensions. Furthermore, the terms LED and light-emitting diode are used synonymously here.

Embodiments relate to a printed circuit board or board, which is provided with a plurality of through openings. The apertures typically each have approximately the same shape as the effective radiating area of a single LED, but are larger, e.g. each about 5% to about 30% in length and width. For example, the openings 70 may have the same shape as the effective radiating area of the LED but be 1 mm or 2 mm in diameter larger than this. The shape of the openings 70 may also correspond to the shape of the surface of the emitting side of the LEDs, but be about 1 to 3 mm smaller than this. The LEDs are mounted on the printed circuit board so that their light emitting side faces the printed circuit board or is attached to a first side of the printed circuit board or printed circuit board, so that the light emitted during operation radiates through the openings of the printed circuit board and on a second side of the printed circuit board PCB / board exit. The usually planar (non-light-emitting) back side of the LEDs is correspondingly raised in relation to the surface of the printed circuit board, with the individual rear sides of the LEDs typically lying on a common plane. The contacting of the individual LEDs to the printed circuit board can be provided in various methods known to the person skilled in the art.

At the common one-level rear sides of the LEDs, a metal plate is attached, typically made of aluminum or another good heat-conducting material such as copper. In this case, a thin (typically less than 0.5 mm) applied means for improving the heat transfer can be provided between the LED backs and the metal plate, typically thermal grease.

In operation, the LEDs emit light through the holes of the circuit board. Due to the comparatively small thickness of the printed circuit board in comparison to the size of the openings or by appropriate coordination between emission characteristic of the LED and the opening size, a reduction of the emission angle can be prevented or minimized become. The heat loss of the LEDs is in each case passed over their entire (typically planar) back into the metal plate or the heat sink, whereby a highly efficient cooling is achieved. The metal plate should have a sufficient thickness, typically at least about 2 mm, to ensure sufficient dissipation of the heat loss from the contact area with the LED. On the other hand, if the metal plate were not sufficiently thick or made of material which is not sufficiently thermally conductive, the removal of heat energy from the contact zone with the LED could not be sufficient. The thickness of the plate may be in embodiments of 2 mm to 10 mm, in particular from 3 mm to 7 mm.

The appropriate choice of material for the metal plate and their geometric design are determined depending on the power loss of the individual LEDs and their number per conductor or metal plate. The execution of appropriate design experiments and calculations or thermal simulations is part of the standard knowledge of the skilled person.

Fig. 1 shows an LED lighting module 10 according to embodiments in a plan view. Between the aluminum plate 20 and the printed circuit board (also referred to as board below) 30, eight light-emitting diodes (LEDs) 40 are arranged in two rows of 4 LEDs each. The LEDs are slightly larger (their outline lines hidden in the board are in Fig. 1 Dashed lines) as the openings 70 in board 30. About arranged in the board traces 60, the terminals of the LEDs 40 are guided to one side of the board, where they are completed with a multi-pin socket 50 which is mounted on the board. The interconnects 60 extend in the view of Fig. 1 on the side facing away from the viewer surface of the board 30, on which the LEDs are mounted. Other geometrical arrangements are also possible, as described below.

In exemplary embodiments, the conductor tracks 60 can also run on the other side of the board 30, ie in the Fig. 1 on the side of the board facing the viewer. If the board 30 has several layers, that is a multilayer board, the printed conductors can also run in an intermediate layer of the board. Also mixed forms between the above are possible. Depending on the design, feedthroughs may be provided from the printed conductors through the printed circuit board or part of the printed circuit board to the LEDs. The board 30 is, typically at its corners, with post / spacers 80 with the Aluminum plate 20 connected, which serves as a heat sink. The light emission of the LEDs is directed in this representation of the drawing plane to the viewer.

Fig. 2 shows a schematic side view of the LED lighting module of Fig. 1 , Thermal paste (not shown) provides improved heat transfer between the housings of the LEDs 40 and the aluminum plate 20. The holes 70 in the circuit board are shown in phantom. The emission direction of the LEDs 40 is shown schematically by arrows in the example of the left of the four illustrated light emitting diodes. The emitted light passes through the apertures 70 in the circuit board 30, that is, the light passes through the circuit board 30 through the apertures 70. In other embodiments, for example, the LEDs are fitted in additional recesses in the circuit board 30 rather than in FIG Fig. 2 shown mounted on the surface, the emitted light traverses only a portion of the thickness of the board, for example, 30%, 50% or 70% of the thickness of the board (not shown).

In embodiments, the apertures 70 are typically from about 5% to about 30% larger (by diameter) than the effective radiating area of the light emitting diode 40, or a projection of the radiating surface of the light emitting diode onto the plane of the circuit board. The dimensions of the openings are to be chosen so that on the one hand, the opening is large enough not to block the radiated light, on the other hand, the opening is smaller than the base of the LED on its emission side, since the LED rests on its edges on the board ,

In embodiments, an LED lighting module 10 may include from 1 to 64 light emitting diodes 40 and as many holes / openings 70, typically arranged as an mxn matrix, such as (non-limiting) 1 x 1, 1 x 2, 2 x 2, 2 x 3, 2 x 4, 4 x 4, etc.

If the LEDs 40 used have a different shape from that described here of a flat cuboid, this may require changes to the structure described, which represents a standard task for a person skilled in the art. Thus, a non-planar back side of the LEDs could require corresponding recesses in the heat sink 20 in order to ensure a corresponding surface contact between LED and heat sink, and thus good heat dissipation.

Fig. 3 shows a lighting fixture 130, in which three LED lighting modules 10 (shown only schematically here) according to embodiments in a lamp housing 110 are installed. The three modules 10 are connected via cable 140 to a ballast 120, which is designed to transform the 115 or 230 volt AC mains voltage to the operating voltage of the modules 10, typically from 6 to 120 volts DC, eg 6, 12, 24, 48 , 60 or 96 volts. Typically, the ballast 120 is designed as a switching power supply. In order to ensure good heat dissipation from the LED modules 10 to the surroundings of the lamp 130, the aluminum plates 20 can be connected / bonded in a planar manner to an inner wall of the housing 110 using thermal paste. The power supply may additionally be equipped with control functions to enable single switching on / control of individual LEDs or of groups. Any number of lighting modules 10 may be incorporated into a common housing 110 limited only by its dimensions and the performance of the one or more ballasts 120. The LED modules 10 may be configured to be connected through the connector 50 also in FIG Position are kept and thus easily replaceable. An additional clamping device or the like may also be provided to ensure thermal contact with the housing 110.

In the Fig. 4 is a side cross-sectional view of a similar embodiment as that of Fig. 3 shown.

Fig. 5 shows a further embodiment, analogous to that of 3 and 4 , In this case, two LED lighting modules, each with four LEDs 40 are mounted in a housing 110. The two modules are each powered by a ballast 120, 121 with DC voltage. The two ballasts are connected to a common neutral conductor 132. The connections for the mains alternating voltage 133, 134 can, as shown, be designed separately for both ballasts 120, 121. If these are connected to different phases of the supply current network, a simple circuit of the illuminance can be realized in this way. By switching off one of the two (in other embodiments, one or two of three) phases, the illuminance can be reduced without the need for a separate switching device or electronics in the lamp housing. In further embodiments, see, for example Fig. 6 below, several ballasts per lighting module 10 may be provided.

Fig. 6 shows an embodiment of an LED lighting module 10 similar to that of Fig. 1 , In this case, eight LEDs are combined in two groups of four LEDs connected in series. The connections are led separately to the sockets 50, 51, so that both groups can optionally be switched or controlled separately, analogously to the example in FIG Fig. 5 For example, with different ballasts, which may optionally be connected to different phases. A side view of this embodiment substantially corresponds to the illustration in FIG Fig. 2 , The LEDs 40 and typically the tracks 60 are located in this example on the side facing away from the viewer side of the board 30, but are shown for illustrative purposes. For other possible levels of the conductor tracks the same applies as in Fig. 1 described. A combination of two such modules, each with 8 high-power LEDs, each about 6 to 9 W, in a lamp housing is suitable from the achieved luminance, for example as a lighting fixture for street lighting purposes.

Fig. 7 schematically shows embodiments in which a plurality of LEDs 40 are arranged in a circular or star-shaped arrangement on the first side of the board 30. As a result, possibly any existing directional radiation characteristics of the LEDs can be partially compensated, whereby the uniformity of the angular distribution of the light output increases.

In exemplary embodiments, the light-emitting diodes 40 are high-power light-emitting diodes. These are typically cuboid with a low height-to-width ratio, but may be e.g. also have a round or elliptical form factor. Here height refers to the dimension in the main or symmetry direction of the light emission. Preferably, the height is less than 20% of the respective larger of width and length. Typical size ranges are 0.5 to 8 mm height (measured without any optical attachment element), more particularly 1 mm to 3 mm, and each (independently of each other) 5 to 120 mm in length and width, more particularly 8 mm to 30 mm. An exemplary, non-limiting LED may have dimensions of 12 x 15 x 1.6 mm (L x W x H) and a power consumption of 7 W. Typical power consumption is 1 W to 100 W, more specifically 3 W to 50 W.

Lighting fixtures according to embodiments using LED modules 10 as described may further include a blower 200. This blows or sucks air in the Gap or air space 205 between board 30 and heat sink 20 to increase the cooling, which in Fig. 8 is shown.

Lighting fixtures according to embodiments may further comprise a thermosyphone 210 or a heat pipe 220, which is in thermal communication with the backside of the LEDs. For this purpose, the heat sink 20 may be arranged as in previous examples, and in addition to the thermosyphone 210 or the heat pipe 220 are in communication, so that the waste heat is transported to a heat sink / condenser 230. This is in Fig. 9 shown schematically. Both elements 210, 220 may be thermally connected directly to the LED backs without heat sink 20.

The LED modules according to embodiments are suitable as replaceable lighting fixtures as a replacement for conventional illuminants such as halogen bulbs or rods. For this purpose, the connection can be made to the power supply via plug, so that the module can be quickly and easily replaced by laymen in case of a defect or to change the illuminance. In addition, the power connector may be configured to hold the module in position at the same time, such as by combination with the posts / spacers 80. In embodiments, the heat sink 20 may be part of the module 10, or part of the lamp 130.

The features of the invention disclosed in the foregoing description, in the claims and in the drawings may be essential both individually and in any technically meaningful combination for the realization of the invention in its various embodiments.

Claims (15)

LED lighting module (10) comprising: a circuit board (30) having a first and a second side and at least one through opening (70), at least one light emitting diode (40) mounted on the opening (70) on the first side of the circuit board (30) and having a light emitting front side and a non-emitting rear side, wherein the light-emitting diode (40) is mounted with its light-emitting front side on the first side of the board so that emitted light passes through at least a part of the opening (70) and exits on the second side of the board, and that the back side of the light-emitting diode is exposed in that the module (10) with the non-light-emitting rear side of the light-emitting diode (40) can be attached to a heat sink (20). LED lighting module (10) according to claim 1, wherein the circuit board (30) conductor tracks (60), and wherein the contacting of the light emitting diode (40) to a conductor track (60) on the side of the board (30) is arranged, which Direction of light emission is opposite. The LED lighting module (10) of claim 1 or 2, wherein the opening (70) is smaller than a base of the light emitting diode (40). The LED lighting module (10) of any one of the preceding claims, wherein the aperture (70) is 5% to 30% larger than the effective emitting area of the LED. LED lighting module (10) according to one of the preceding claims, comprising 1 to 64 light-emitting diodes (40) and 1 to 64 openings (70) for the light-emitting diodes. The LED lighting module (10) of any one of the preceding claims, further comprising a heat sink (20), wherein the light emitting diode (40) is disposed between the board (30) and the heat sink (20) is mounted, and a light emitting front side of the light emitting diode (40) facing the circuit board (30). The LED lighting module (10) of claim 6, wherein the heat sink (20) is a metal plate. The LED lighting module (10) according to claim 6 or 7, wherein the distance between the board (30) and the heat sink (20) substantially corresponds to the extension of a light emitting diode in the direction of its light emission. LED lighting module (10) according to any one of claims 6 to 8, wherein between the heat sink (20) and the first side of the board (30) consists of an air volume (205). LED lighting module according to one of the preceding claims, wherein a plurality of light emitting diodes (40) are arranged in an m x n matrix on the first side of the board (30). LED lighting module according to one of claims 1 to 9, wherein a plurality of light-emitting diodes (40) are arranged in a circular or star-shaped arrangement on the first side of the board (30). LED lighting module according to one of the preceding claims, wherein the light-emitting diodes are cuboid high-performance light-emitting diodes with a low height-to-width ratio, preferably the height is equal to or less than 20% of the respective larger of width and length. Lighting fixture with an LED lighting module (10) according to one of claims 1 to 12. The lighting fixture according to claim 13, further comprising a fan (200), wherein between the circuit board (30) and the heat sink (20) there is an air volume (205) into which cooling air is blown by means of the blower (200). The lighting fixture of claim 13, further comprising at least one of the items in the list: a thermosyphone (210), and a heat pipe (220) in thermal communication with the back side of the LEDs (40).

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