AT13372U1 - LED module with high luminous flux density - Google Patents

Abstract

The invention relates to an LED module, comprising: at least one LED chip on a carrier, and a phosphor layer, which is applied to the light emitting surface of the LED chip, wherein the phosphor particles are accommodated in a matrix 4 in the layer wherein the concentration of the phosphor particles is substantially constant in a first region covering and / or laterally surrounding the LED chip, such that the color conversion particles are densest packed in that region, and in a second, the first Area adjacent area abruptly drops with a second gradient.

Description

Austrian Patent Office AT13 372U1 2013-11-15

description

LED MODULE WITH HIGH LIGHT CURRENT DENSITY

The present invention relates to LED modules in particular COB (chip-on-board) LED modules, with high-density LED chip packaging and LED lights, such as. Spotlights, downlights that have such modules.

Under "LED module " is to understand at least one LED (LED-the or SMD LED) on a support, such as a printed circuit board (PCB), an SMD carrier, etc.

The invention particularly relates to LED modules for generating white light. For this purpose, it is well known to arrange a monochromatic, in particular blue or blue / UV or UV LED on a support and further provide a color conversion material that converts a portion of the light emitted by the LED light in another, especially longer wavelength light. The vote between color conversion material and emission spectrum of the LED is chosen such that the resulting mixed light comes close to the Plank curve in CIE diagram and can be described as white.

In particular, in LEDs which emit a large amount of light power, which is suitable for the conversion in color conversion materials, occurs due to the conversion of primary emitted light into heat energy and longer-wave light, in the color conversion materials on a considerable heat output, which only poorly over the surrounding matrix materials (eg silicones or polymers) can be dissipated in which the phosphor particles are embedded, since matrix materials normally have a low thermal conductivity.

Use of filler particles in the matrix material or a highly concentrated phosphor layer in the vicinity of the LED chip can significantly improve the heat dissipation. The concentration / amount of Fillerpartikel is limited on the one hand by the method of application of the phosphor paste, on the other hand by the light absorption of the particles, which reduces the light output. Another way to increase the heat dissipation is the use of inorganic matrices, for example. ceramic materials, glass (eg, ceramic phosphor chips), or phosphor particles coated with ceramic materials. With the last-mentioned method, a high luminous flux density can be achieved without overheating the phosphor particles if the heat conductivity and / or the thermal connection to the heat sink is / are sufficient. However, the adjustable / achievable hues are limited and a high amount of phosphor chips is required, which trigger expensive logistic processes. In addition, the types of applicable LED chips are limited for the reasons mentioned above.

It is an object of the present invention to improve the heat dissipation away from the Farbkonversi onsschicht.

This object is solved by the features of the independent claims. The dependent claims further form the central idea of the invention in a particularly advantageous manner.

By a dense packaging of the phosphor over and / or the LED chips (in a certain proximity of the LED chips), a sufficient heat dissipation can be realized. When the heat dissipation of the LED chips is solved, the packaging density of the LED chips can be significantly higher than in the prior art LED modules with homogeneous phosphor particle distribution in the matrix around and / or via the LED chips. A certain limitation occurs with light emission of 10 lm / mm 2 because of the heat generation of the phosphor, since the matrix material can be heated at about 25-35 ° (depending on the phosphor / the CCT / CRI). The doubling of the luminous flux density causes the increase in the temperature 50 ° -70 ° of the Tc temperature in relation to the Tc point and / or limits the maximum allowed temperature at the Tc point for products in which a long-term reliability is required, 1 / 16 Austrian Patent Office AT13 372U1 2013-11-15 and / or failures due to the formation of cracks in silicones at higher temperatures. At a typical Tc temperature of ~ 90 ° C and a long-term stability of 130 * Ό for the silicone, some limitations of luminous flux density arise, which can easily be eliminated with higher light-emitting surfaces, but this leads to much larger reflectors and higher material costs Construction of the luminaire.

Luminous flux can be realized from 2500 Im at 10 lm / mm2 luminous flux density, with an emitting area of 19mm diameter. With a diameter of 25mm, a luminous flux of 5000 Im can be achieved. The luminous flux values mentioned are common to general lighting.

With a dense / concentrated phosphor layer according to the invention a light-current density of up to 100 Im / mm2 of the module can be achieved when the heat dissipation of the LED chips and their environment is treated. At such high luminous flux density, the packaging density of the LED chips is limited because of the thermal management of the LED chips themselves and the necessary electrical connections.

A luminous flux density of 10 lm / mm2 can be achieved with a density of 40mW-60mW of blue light per mm2. This can be prepared with 1 a low-power LED chip with 0.2mm2 per 1mm2 or a mid-power LED chip with 0.5mm2 per 4mm2. Packing density It means a packing density of 30% -50%, which is dependent on the chip size of the existing area of the module surface. Depending on the operating current, this leads to 200mW / mm2-300mW / mm2, which corresponds to 25 lm / mm2 - 75 lm / mm2 (2700K, CRI95, 200mW / mm2 -6500K, CRI70, 300mW / mm2). For standard application ~ 50 mm2 / mm can be adopted and the diameter for the 2500mm module can be reduced to ~ 8mm diameter and for the 5000mm module to ~ 11mm. This results in significant smaller reflectors since the reflector size is linearly proportional to the light emitting surface.

A first aspect of the invention relates to an LED module, comprising: at least one LED chip on a support, and [0014] a phosphor layer which is applied to the light emission surface of the LED chip, Wherein in the layer the phosphor particles are accommodated in a matrix 4, wherein the concentration of the phosphor particles [0017] - in a first region which covers and / or laterally surrounds the LED chip is substantially constant, in such a way that the color conversion particles are packed as densely as possible in this area, and - in a second area adjoining the first area, it drops abruptly with a second gradient.

The LED module may further comprise a dam.

The support of the LED module may be prepared by a metal plate, preferably an aluminum numplatte and a printed circuit board.

The LED module can have a luminous flux density of at least 18 lm / mm 2, preferably 20-100 lm / mm 2, particularly preferably 25-75 lm / mm 2.

The thickness of the second region may be between 12pm and 40pm, preferably between 20pm and 30pm.

A second aspect of the invention relates to an LED module, comprising: - at least one LED chip on a support, and [0025] - a phosphor layer, which on the light emitting surface of the LED chip (1) wherein in the layer phosphor particles and optional scattering particles are accommodated in a matrix, wherein the phosphor particles are strongly compressed in a layer adjacent to the LED chip.

The matrix 4 may comprise a polymer from the group of silicone materials and epoxy materials.

The LED module may be a COB module.

The dam can laterally surround the LED chip or a plurality of LED chips, and the LED chips preferably project beyond the height, and preferably the matrix 4 can coat the upper side of the LED chip.

The LED module may have an additional phosphor plate preferably with homogeneous phosphor particle distribution.

The average diameter of the dye particles may be between 5pm and 15pm.

The average diameter of the scattering particles can be between 0.5 pm and 2 pm.

At least the inner wall of the dam may be light-reflecting or scattering, and / or the dam may have reflective or light-scattering particles, preferably white pigments.

Another aspect of the invention relates to LED light, in particular spotlights or downlights, having at least one LED module of the type described above.

Further features, advantages and features of the invention will now be explained with reference to the following description of an embodiment and the figures of the accompanying drawings.

Amber, red, green, and / or blue LED chips (for example RGB) or blue and red LEDs for producing monochromatic, white or differently colored, mixed light can be used as the LED chips. Further, the LED chip may have a photoluminescent material disposed over the LED chip, such as inorganic phosphor (s) (for example, garnets: YAG: Ce3 +, LuAG: Ce3 +, orthosilicates (BOSE): (Ca, Sr, Ba) 2Si04 : Eu2 +, (Ca, Sr) 2Si04: Eu2 +, (Sr, Ba) 2Si04: Eu2 +, (Ca, Ba) 2Si04: Eu2 +; Nitrides: CaAISiN3: Eu2 +, (Sr, Ca) AISiN3: Eu2 +, CaAISiON3: Eu2 +, ß -SiAION: Eu2 +)) and / or organic phosphor (s) may be provided, by means of which the light emitted by the LED chip and the light converted in the photo-luminescent material are mixed together such that any desired color or white Light (eg. By means of blue LED and yellow (and / or green and / or red) phosphor) can be generated. Any combination of the aforementioned LED chips in the LED module 1 is also conceivable.

Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6A-C As in Fig. 1, a schematic sectional view of a stall is shown the technology LED module, shows a schematic sectional view of an LED module according to the invention according to the first embodiment, shows the concentration profile of the scattering particles or Farbkonversionspar-particles of an LED module according to the invention, shows a schematic sectional view of an LED module according to the invention according to the second embodiment, shows a schematic sectional view of an LED module according to the invention according to a further embodiment, and shows the manufacturing process of an LED module according to the invention. 1, a state of the art LED module 1 with at least one LED chip 2, which is mounted on a support 3, has at least one surface. The LED chips 2 are placed within a dam 5. The phosphor particles (symbolized with small dots) are distributed homogeneously in the matrix 4 above and around the LED chip 2. The matrix 4 is bounded by the dam 5.

FIG. 2 shows an inventive LED module 1. As shown schematically in FIG. 2, phosphor particles 6 are highly concentrated in a layer 8, which layer 8 covers the LED chips 2 above and / or laterally. The thickness of the phosphor layer 8 may be, for example, from 1 to 10 times, preferably 4-6 times the diameter of the phosphor particles. Dam 5 may contain reflective (white) particles (eg, TiO 2, SiO 2, Al 2 O 3, BaTiO 3, etc.).

Fig. 3 represents the concentration of the dye particles 6. It decreases starting from the layer 8 in the direction away from the LED chip 2 abruptly, so that it is almost zero outside the layer 8.

Optionally, scattering particles 7 can be used in the matrix 4. Superimposed on this very steep gradient gradient of the dye particles 6 is a substantially flatter and continuous gradient of scattering particles 7, so that the concentration of the scattering particles 7, also seen away from the LED, decreases steadily. In addition, known additives which influence the viscosity (for example SiO 2, Al 2 O 3, TiO 2) can be incorporated in the matrix 4.

Fig. 4 shows a second embodiment of the invention. The carrier 3 can be prepared as a flexible substrate by a metal plate 10 (gold or aluminum plate) and a printed circuit board 9 preferably FR4. The application of Metalkernplatinen is also conceivable. Since the module size is much smaller compared to the standard structure, the mounting of the module 1 on a heat sink with good thermal connection is possible without bending.

Fig. 5 shows a further embodiment of the invention, wherein an additional phosphor plate 11, which is used as a color correction element, is integrated. The concentration of the phosphor (s) is homogeneous in the phosphor plate 11. The phosphor plate serves to finely adjust / shift the first color tone / color spot generated by the phosphor layer 8 in a second step. The phosphor plate may optionally contain scattering particles.

In the production of the phosphor layer 8, a densely packed color conversion layer, for example, by settling in which the particles move slowly due to gravity, at least temporarily reducing the viscosity of the silicone matrix, etc., is provided. In this mechanical approach, the dye particles are substantially contiguous and, in any case, densely packed. If necessary, a thin pellicle or another thin separating layer of the matrix material may be present between the individual dye particles. Due to the direct contact of the dye particles, the thermal conductivity of this layer increases abruptly.

Upon settling, the movement of the particles is slow and the resulting phosphor layers 8 emit different hues. The settling process can be accelerated in a linear fashion or, more generally, by centrifuging (See Figures 6A-C). The disadvantage of centrifuging is the forces occurring in plane 12 (See Fig. 6A). These are particle size dependent and cause non-homogeneity of the distribution of the particles. There are more particles on the edge of the LED module than in the middle. This can be done using the larger centrifuges, but they have the disadvantages of introducing expensive process operations. LED modules with inhomogeneous and homogeneous phosphor layer thicknesses 13, 14 are prepared by using rigid carriers on FIG. 6B. One possible solution according to this invention is the use of flexible (circular) substrates as support 3 (see Fig. 6C), e.g. Lead frame with about 0.3-0.8mm thickness (preferably 0.4-0.6mm) or a Me-talker board with a similar thickness. The selected centrifuge size is dependent on the allowed bending radius of the substrate 3. A course of the production according to the invention can thus be as follows: mixture of a silicone paste with or without the viscosity-influencing aggregates, [0053] one or two several color conversion substances (for example, yellow, green, red or

Mixtures thereof) and, if appropriate, with scattering particles, dosing a quantity of this mixture onto the LED module / modules, for example by dispensing, [0055] mechanical compacting of the dye particles, for example by centrifuging, [0056] Curing, optional singulation of the LED module.

As can be seen in particular in FIG. 3, in principle the concentration of the dye particles 6 PH and the concentration of the optional scattering particles 7 STR decreases from the upper side / side of the LED chip 2 and the thickness d of the layer decreases.

In a first region 0-di, the concentration of the densely packed dye particles 6 PH is substantially constant, i. for example, it decreases to 90% in this area. This first area is followed by a second area between D1 and D2, where the concentration decreases abruptly, for example to a value of 10%.

In contrast, the gradient of the scattering particles STR is substantially constant and substantially flatter in comparison to the abrupt drop in the concentration of the dye particles PH in the second region, ie between d1 and d2.

The course of the concentration of the scattering particles 7 STR is comparable by a concentration course as it can be achieved for example by sedimentation of the heavier scattering particles STR in the silicone matrix 4. In contrast, the course of the dye particles 6 PH is typical for compaction to saturation, i. until the closest possible packing of the dye particles 6 PH in the layer 8.

Preferably, the second region between d1 and d2 in which there is a drop in the concentration of the dye particles 6 PH from, for example, 90% of the maximum concentration to 10% of the maximum concentration, a thickness which is less than 50%, preferably less than 25%. of the first region, ie between 0 and d1, in which first region the dye particle concentration is substantially constant.

The range from 0 to d1, that is to say the drop in the concentration of the dye particles 6 to 90%, can be, for example, 50 ppm.

The transition region between d1 and d2, ie for the drop from 90% concentration to 10% concentration of the dye particles, may for example have a thickness of 25 pm.

The average diameter (d.sub.50 value) of the scattering particles can be, for example, 1 .mu.m, which is substantially less than the average diameter of the dye particles, which can be, for example, between 5 pm and 10 pm. All averages in the present specification refer to d50 values of diameters.

The dye particles according to the invention have a higher density such as scattering particles. 5/16 Austrian Patent Office AT 13 372 Ul 2013-11-15

LIST OF REFERENCE NUMBER 1 LED module 2 LED chip 3 carrier 4 matrix 5 dam 6 phosphor particles 7 scattering particles 8 phosphor layer 9 metal plate 10 circuit board 11 phosphor plate 12 In-plane forces 13 LED module with inhomogeneous phosphor layer 14 LED module with homogeneous phosphor layer 15 flexible substrate 6/16

Claims (14)

Austrian Patent Office AT13 372U1 2013-11-15 Claims 1. LED module (1), comprising: - at least one LED chip (2) on a carrier (3), and - a phosphor layer (8) arranged on the light emitting surface of the LED chips (2) is applied, wherein in the layer (8) the phosphor particles (6) are accommodated in a matrix 4, wherein the concentration of the phosphor particles - in a first area which covers the LED chip (2) and / or laterally surrounding substantially constant, such that the color conversion particles are packed in this area as close as possible, and - in a second, adjacent to the first area area abruptly drops with a second gradient. 2. LED module according to claim 1, wherein the LED module (1) further comprises a dam (5). 3. LED module according to one of the preceding claims, wherein the carrier (3) is prepared by a metal plate, preferably an aluminum plate and a printed circuit board. 4. LED module according to one of the preceding claims, wherein the LED module (1) has a luminous flux density of at least 18 lm / mm2, preferably 20-100 lm / mm2, particularly preferably 25-75 lm / mm2. 5. LED module according to one of the preceding claims, wherein the thickness of the second region between 12pm and 40pm, preferably between 20pm and 30pm. 6. LED module (1), comprising: - at least one LED chip (2) on a carrier (3), and - a phosphor layer (8) which is applied to the light emitting surface of the LED chip (1), wherein in the layer (8) phosphor particles (6) and optionally scattering particles (7) are accommodated in a matrix (4), wherein the phosphor particles (6) in a layer adjacent to the LED chip (2) are highly compressed. 7. LED module according to one of the preceding claims, wherein the matrix 4 comprises a polymer from the group of silicone materials and Epoxymateria-Lien. 8. LED module according to one of the preceding claims, wherein the LED module is a COB module. 9. LED module (1) according to one of the preceding claims, wherein the dam (8) laterally surrounds the LED chip (2) or a plurality of LED chips (2) and the LED chips (2) preferably in height surmounted and preferably the matrix 4 the top of the LED chip (2) coated. 10. LED module (1) according to one of the preceding claims, wherein the LED module (1) has an additional phosphor plate (11), preferably with a homogeneous phosphor particle distribution. 11. LED module according to one of the preceding claims, wherein the average diameter of the dye particles is between 5pm and 15pm. 12. LED module according to one of the preceding claims, wherein the average diameter of the scattering particles is between 0.5 pm and 2 pm. 7/16 Austrian Patent Office AT13 372U1 2013-11-15 13. LED module (1) according to one of claims 9 to 12, wherein at least the inner wall of the dam (5) is light-reflecting or scattering, and / or the dam has reflective or light-scattering particles, preferably white pigments. 14. LED light, in particular spotlights or downlights, comprising at least one LED module (1) according to one of the preceding claims. For this 8-sheet drawings 8/16