LED MODULE

Abstract

The invention relates to a method for producing an LED module (1) and comprises at least the following steps:providing at least one LED chip (4) on a substrate material (2), anddispensing a not-cured (flowable/liquid) potting compound (3) on top of the LED chip (4), said potting compound (3) containing at least one type of luminescent particles and preferably a matrix material. During the step of dispensing, a predetermined potential is applied directly or indirectly to at least one LED chip (4).

Claims

1. An LED module produced by a method comprising: providing at least one LED chip (4) on a carrier material (2), dispensing a non-cured liquid potting compound (5) above the LED chip (4), wherein the potting compound (5) contains at least one type of phosphor particles and preferably a matrix material, wherein a predetermined potential is applied to at least one LED chip (4) directly or indirectly during the dispensing of the potting compound (5).

2. The LED module (1) produced according to the method as claimed in claim 1, wherein applying the predetermined potential is carried out by short-circuiting electrical terminals of the at least one LED chip (4) while the phosphor particles sink in the liquid potting compound (5).

3. The LED module (1) produced according to the method as claimed in claim 1, wherein applying the predetermined potential is carried out by applying an AC voltage to electrical terminals of the at least one LED chip (4) while the phosphor particles sink in the liquid potting compound (5), wherein the voltage and the frequency of the AC voltage are selected such that the phosphor particles sink substantially linearly in the liquid potting compound (5).

4. The LED module (1) produced according to a method as claimed in claim 1, wherein applying the predetermined potential is carried out by applying a DC voltage to electrical terminals of the at least one LED chip (4) while the phosphor particles sink in the liquid potting compound (5), in order to deflect the phosphor particles at least partly in a direction of the LED chips (4).

5. The LED module (1) produced according to the method as claimed in claim 1, wherein applying the predetermined potential is carried out by arranging the LED module (1) within a magnetic field while the phosphor particles sink in the liquid potting compound (5), wherein alignment and strength of the magnetic field are selected such that the phosphor particles sink substantially linearly in the liquid potting compound (5).

6. The LED module (1) according to the method as claimed in claim 1, wherein, during the dispensing process, at least the region of the potting compound (5) is shielded from light in a region of an excitation spectrum of the phosphor particles and a predetermined potential is applied indirectly to at least one LED chip (4).

7. An LED module (1) produced according to a method comprising: providing a module plate (2), with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; dispensing a liquid potting compound (5) onto the at least one LED chip (4), wherein the potting compound (5) comprises phosphor particles; darkening the at least one LED chip (4) in such a way that at least in the absorption spectrum of the at least one LED chip (4) no light passes to the at least one LED chip (4) at least during the sinking of the phosphor particles in the liquid potting compound (5) and a predetermined potential is applied indirectly to at least one LED chip (4).

8. The LED module (1) as claimed in claim 1 wherein the entire LED module is darkened at least during the sinking of the phosphor particles.

9. The LED module (1) as claimed in claim 1, wherein the LED module (1) is arranged in a darkened environment at least during the sinking of the phosphor particles.

10. The LED module (1) as claimed in claim 1, wherein, at least during the sinking of the phosphor particles, the LED module (1) is arranged in an environment which is illuminated by a light source that emits visible light outside the absorption spectrum of the LED chip (4).

11. The LED module (1) as claimed in claim 1, wherein the at least one LED chip (4) or the LED module (1) is covered by a film that is light-nontransmissive at least in the absorption spectrum of the at least one LED chip (4), the film being a dark or black film (6), at least during the sinking of the phosphor particles.

12. An LED module (1) produced according to a method comprising: providing a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; dispensing a liquid potting compound (5) onto the at least one LED chip (4), wherein the potting compound (5) comprises phosphor particles; wherein, at least during the sinking of the phosphor particles in the potting compound (5), the LED module (1) is arranged obliquely with respect to the horizontal in such a way that the phosphor particles sink substantially linearly in the liquid potting compound (5).

13. An LED module (1) produced according to a method comprising: providing a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; dispensing a liquid potting compound (5) onto the at least one LED chip (4), wherein the potting compound (5) comprises phosphor particles; wherein, at least during the sinking of the phosphor particles in the potting compound (5), the LED module (1) is accelerated in such a way that a distribution of the phosphor particles that is as homogeneous as possible is provided at least around the region of the at least one LED chip (4).

14. An LED module (1) produced according to a method comprising: providing a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; dispensing a liquid potting compound (5) onto the at least one LED chip (4), wherein the potting compound (5) comprises phosphor particles; wherein, after the sinking of the phosphor particles in the liquid potting compound (5), a directional flow is generated in order to provide a distribution of the phosphor particles that is as homogeneous as possible at least around the region of the at least one LED chip (4), wherein the flow is generated in the liquid potting compound (5) by a steering device arranged in the liquid potting compound (5), in particular a microstirrer.

15. The LED module (1) produced according to a method as claimed in claim 1, wherein, during the sinking of the phosphor particles in the liquid potting compound (5), the LED module (1) is operated at intervals by applying the predetermined potential in such a way that the potting compound (5) cures layer by layer on account of light emission.

16. An LED module (1) produced according to a method comprising: providing a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; sieving phosphor particles onto the at least one light field; dispensing a liquid potting compound (5) onto the at least one LED chip (4).

17. An LED module (1) produced according to a method comprising: providing a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least one LED chip (4) is arranged within the light field; applying phosphor particles onto the at least one light field by means of a spray mist coating step; dispensing a liquid potting compound (5) onto the at least one LED chip (4).

18. The LED module (1) as claimed in claim 1, further comprising: a module plate (2) with at least one dam (3) which delimits at least one light field, wherein at least two linearly arranged LED strings each having a plurality of series-connected LED chips (4) are provided within the light field; and wherein the LED strings are arranged with alternating polarities in the at least one light field.

19. The LED module (1) as claimed in claim 1, further comprising: a module plate (2) with at least one dam (3) which delimits at least one light field, wherein a plurality of LED chips (4) are provided within the light field; and wherein the LED chips (4) are arranged in alternating polarity with respect to one another in the at least one light field.

20. The LED module (1) as claimed in claim 1, wherein the phosphor particles are from inorganic phosphor particles.

21. The LED module (1) as claimed in claim 1, wherein the liquid potting compound (5) is a silicone-based or epoxy-based or both silicone- and epoxy-based potting compound (5) and is transparent in the cured state.

22. The LED module (1) as claimed in claim 1, wherein the liquid potting compound (5) is applied by a dispensing method.

23. The LED module (1) as claimed in claim 1, wherein the dam (4) has a width as seen in plan view of between 50 m and 2 mm.

24. A lighting device, comprising at least one LED module (1) as claimed in claim 1.

25. A method for producing an LED module (1), said method comprising: providing at least one LED chip (4) on a carrier material (2), dispensing a non-cured (flowable/liquid) liquid potting compound (3) above the at least one LED chip (4), wherein the potting compound (3) contains at least one type of phosphor particles and a matrix material, wherein a predetermined potential is applied to at least one LED chip (4) directly or indirectly during the dispensing process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0091] A detailed description of the figures is given below, wherein:

[0092] FIG. 1 shows a schematic view of a first embodiment of an LED module according to the invention during the production process;

[0093] FIG. 2 shows a schematic view of a second embodiment of an LED module according to the invention during the production process;

[0094] FIG. 3 shows a schematic view of a third embodiment of an LED module according to the invention during the production process; and

[0095] FIG. 4 shows a schematic view of a fourth embodiment of an LED module according to the invention during the production process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0096] An explanation is given below of one preferred embodiment of an LED module 1 together with the methods particularly preferred in each case for producing such an LED module 1 with reference to FIGS. 1 to 3.

[0097] A first step involves providing a module plate 2 with a (at least one) dam 3, which preferably demarcates a substantially circular light field. A multiplicity of LED chips 4 are arranged within the light field.

[0098] For the sake of better clarity, a reference sign is assigned by way of example only to one LED chip in each case in the figures. The LED chips 4 here are particularly preferably arranged in rows and columns in the light field, such that a substantially homogeneous distribution of LED chips 4 on the light field can be achieved. As an alternative to the circular dam 3 shown here there is also the possibility of providing a plurality of interconnected or respectively separately arranged dams on the module plate 2.

[0099] Preferably, the dam 3 has a width as seen in plan view of between 50 gm and 2 mm. The dam 3 here can either be formed directly on the module plate 2 or firstly be produced as a separate component that is subsequently connected to the module plate 2.

[0100] Depending on the application, blue-luminous LED chips, red-luminous LED chips, green-luminous LED chips, yellow-luminous LED chips, LED chips that are luminous in the UV range, or a mixture thereof can be used as LED chips 4.

[0101] In a further step, a flowable potting compound 5 is introduced into the light field (or into the light fields), wherein the potting compound 5 is admixed with phosphor particles (distributed therein as homogeneously as possible). If a plurality of light fields are provided, different potting compounds having different phosphor particles or different phosphor particle mixtures can also be used, of course. The liquid or flowable potting compound 5, preferably a silicone- and/or epoxy-based potting compound, here is preferably applied by means of a dispensing method. After the filling of the light field with the flowable potting compound 5, the phosphor particles mixed into the latter begin to sink within the potting compound 5 on account of the gravitational force and deposit at and around the LED chips 4.

[0102] As already explained above, the phosphor particles are positively charged during the mixing process in the potting compound, such that they can be deflected during the sinking in the potting compound by an electric field which can build up between the electrodes of the LED chips on account of the photoelectric effect. This can result in a certain segregation effect that can lead to an inhomogeneous distribution of the phosphor particles and thus to an inhomogeneous light emission of the LED module.

[0103] FIGS. 1 to 4 then show particularly preferred, different solutions that can reduce or prevent such a segregation effect.

[0104] A solution shown in FIG. 1 can be provided by at least the LED chips 4 being darkened during the sinking process, such that no or only a considerably reduced photoelectric effect occurs, such that no or a considerably reduced deflection of the positively charged phosphor particles occurs. Such darkening is hence a form of indirectly applying a predetermined potential to the LED chips 4. Such darkening can be carried out for example by a film 6 (preferably a dark or black film) arranged on the LED module 1. The film 6 here is arranged on the LED module 1 after the filling with the potting compound 5 in such a way that at least the LED chips 4 are covered and thereby darkened. The film 6 here can be embodied in such a way that light can no longer reach the LED chips 4 or the latter can only be reached by light that lies outside the (main) absorption spectrum of the LED chips 4, such that a photoelectric effect no longer occurs or it can be considerably reduced.

[0105] As shown in FIG. 2, there is furthermore the possibility of arranging the LED module 1 within a darkened environment, for example within a darkened channel 10, at least while the phosphor particles sink in the potting compound 5. Instead of such a darkened channel 10, it is also possible to carry out production or the individual steps of production in a correspondingly darkened environment or to effect illumination only with light that emits light that lies outside the (main) absorption spectrum of the LED chips 4, such that a photoelectric effect no longer occurs or it can be considerably reduced. Such production in a correspondingly darkened environment is hence a form of indirectly applying a predetermined potential to the LED chips 4.

[0106] FIG. 3 shows a further possibility for reducing the segregation effect mentioned. As can readily be discerned in FIG. 3, in this solution the LED module 1 is mounted obliquely with respect to the horizontal at least while the phosphor particles sink in the potting compound 5, such that the deflection of the phosphor particles that occurs can be compensated for as far as possible by the gravitational force and the phosphor particles can once again sink as rectilinearly as possible in the potting compound 5 as well. Depending on the charge of the phosphor particles and depending on the magnitude of the electrical potential between the electrodes of the LED chip, the angle of inclination of the LED module during the soaking of the phosphor particles should be adapted accordingly in order to enable a substantially linear sinking of the phosphor particles.

[0107] The LED module 1 in FIG. 4 contains one oras showna plurality of LED chips 4 that can be operated for light emission. By way of example, the LED chips 4 can be designed to emit blue light during operation. However, it is also possible to install LED chips 4 of different types in the LED module 1, which emit light of different colors or wavelengths. The LED chips 4 are applied on a carrier 2, for example a circuit board such as, for instance, a PCB. Preferably, a surface of the carrier 2 on which the LED chips 4 are applied is reflective. Preferably, the LED chips 4 in the LED module 1 are contacted in series by means of bond wires 7. Each LED chip 4 here is preferably connected using at least two bond wires 7. Via the bond wires 7, the LED chips 4 can be supplied with voltage and driven for the operation of the LED module 1. During the method 100 for producing the LED module 1, it is possible to charge the LED chips with the second polarity via the bond wires 7.

[0108] In the LED module 1, the LED chips 4 are arranged in particular within a dam 3. The dam 3 here can at least partly enclose the LED chips 4 as indicated in FIG. 3, for example in a ring-shaped fashion. For the operation of the LED module 1, at least two bond wires 7 are led outside the dam 3 to at least two bond pads 8. The bond pads 8 can furthermore be directly or indirectly connected to an operating voltage source.

[0109] Within the dam 3, the LED chips 4 are embedded into a matrix material, for example a silicone matrix. The LED module 1 is thus preferably produced by means of the dam and fill technique. The matrix material is preferably fully transparent to the light from the LED chips 4 and protects the LED chips 4 and the coatings thereof against external influences. Furthermore, color conversion particles 5 are also provided in the matrix material. The color conversion particles 5 here are deposited in each case with uniform thickness in particular on the surfaces facing away from the carrier 2 and on the side surfaces of the LED chips 4. This is achievable by the above-described method 100 according to the invention.

[0110] The color conversion particles 5 can be for example phosphors that convert the light of the LED chips 4 at least partly in its wavelength. If the LED chips 4 emit in the blue spectral range, for example, then overall white light can be generated by the LED module 1 for example by virtue of a color conversion material that emits in the yellow spectral range for the color conversion particles 5. Different colors and color mixtures of the light emitted by the LED module 1 can be generated by means of a corresponding choice of the color conversion material of the color conversion particles 5 and the type (emission wavelength) of the LED chips 4.

[0111] It can furthermore be seen in FIG. 3 that in the LED module 1 between the LED chips 4 no color conversion particles 5 are deposited on the surface of the carrier 2. The color conversion particles 5 are deposited in particular only on and laterally at the LED chips 4. As a result, the carrier surface between the LED chips 4 is exposed and is preferably designed to be reflective at least there, in order to support and optimize the coupling-out of light from the LED module 1. As is indicated by the arrows in FIG. 3, during the operation of the LED module 1 light emerges from each of the LED chips 4 and then, independently of its emission angle, passes through a layer of color conversion particles 5 that is of approximately identical thickness. This ensures that a very uniform, in particular identically colored light is emitted by each LED chip 4. Consequently, overall the uniformity of the light emitted by the LED module 1 during operation, in particular the color homogeneity of said light over the emission angle, is significantly improved.

[0112] It is also pointed out in addition that color conversion particles 5 can also deposit on the bond wires 7 that connect the LED chips 4 of the LED module 1 to one another. The bond wires 7 are in part even enveloped by color conversion particles 5.

[0113] In order to produce the color conversion coating of the LED chips 4, firstly the color conversion particles 5, preferably mixed in and with the matrix material, are apportioned between the dam 3 and over the LED chips 4. A viscosity of the matrix material is preferably chosen in such a way that the color conversion particles 5 can spread in the matrix material and migrate therein.

[0114] Conventionally, a settling process of the color conversion particles 5 would then begin, in which the color conversion particles 5 would deposit on the surfaces of the LED chips 4 and/or of the carrier 2 in a manner driven purely by the gravitational force before the matrix material is cured.

[0115] According to the invention, however, this settling process is supported or at least influenced by applying a predetermined potential to the LED chips 4. Applying a predetermined potential to the LED chips can be carried out by applying a corresponding voltage such as a DC or AC voltage, for example, to the LED chips 1. That means that at least one defined electric field arises between the LED chips 4 and the color conversion particles 5.

[0116] In addition, a predetermined potential can also be applied to the carrier 2. This can be carried out by applying a voltage to the carrier 2. As a result, by way of example, sinking color conversion particles 5 can be prevented from depositing on the top side of the carrier 2. In particular, the color conversion particles 5 are repelled by the top side of the carrier, such that the coating of the side surfaces of the LED chips 4 is supported further and what is primarily achieved is that the layer on the top side and on the side surfaces of the LED chips 4 is of uniform thickness. This additionally fosters a situation in which the color conversion particles 5 are wholly or largely dispelled from the top side of the carrier 2 between the LED chips 4 and between the outermost LED chips 4 and the dam 3. Said color conversion particles 5 are then forced toward the side surfaces of the LED chips 4 and deposit there on account of the applied voltage. As a result, the interspaces on the top side of the carrier remain largely free of color conversion particles 5 and preferably form reflective areas.

[0117] By way of example, the predetermined potential can be applied by voltage U+ generated by a voltage source 9. A voltage U+ generated by preferably the same voltage source 9 is applied to the LED chips 4 via the bond pads 8 and the bond wires 7. On account of the voltage U+, an electric field can build up on the top side of the LED chips 4, said electric field constraining the charged color conversion particles 5 toward the LED chips 4.

[0118] As a result, the settling process of the color conversion particles 5 can be accelerated and the color conversion particles 5 deposit on the top sides and the side surfaces of the LED chips 4.

[0119] The voltage U+ at the LED chips 4 can preferably be between 20-100 V, more preferably between 40-80 V, even more preferably 60 V.

[0120] By way of example, the predetermined potential can be applied by short-circuiting the bond pads 8 and thus the LED chips 4. What is achieved by short-circuiting the LED chips 4 via the bond pads 8 and the bond wires 7 is that the same potential is present at all the LED chips 4 and also at all parts and electrodes of the LED chips 4. What can be achieved on account of the short-circuiting of the LED chips 4 is that a uniform electric field can build up on the top side of the LED chips 4, and the charged color conversion particles 5 sink uniformly toward the LED chips 4. As a result, the settling process of the color conversion particles 5 can be influenced and the color conversion particles 5 deposit on the top sides and the side surfaces of the LED chips 4. Additionally, or alternatively, the electrical terminals of the at least one LED chip can be grounded. By way of example, the bond pads 8 can be connected to a ground terminal, for example to a reference potential terminal.

[0121] The predetermined potential can also be formed by a changing applied voltage, whereby applied voltages U+ of different magnitudes over time are applied. That means that the electric fields at the LED chips 4 can be set in a targeted manner in each case, preferably even as variable over time. As a result, a quantity and/or a form of deposition of the color conversion particles on the top sides and/or side surfaces of the LED chips 4 can be set with precision, in particular even slightly inhomogeneously over the course of the top side and/or of the side surfaces of the LED chips 1. As a result, the color homogeneity of the finished produced LED module 1 can again be improved. In particular, by means of suitable setting of the voltages U+, it is also possible to perfect the color homogeneity over the emission angle. Here a voltage could moreover also be applied directly to the carrier 2 in order to charge it.

[0122] The invention also relates to a method for producing an LED module 1, said method comprising at least the following steps:

[0123] providing at least one LED chip 4 on a carrier material 2,

[0124] dispensing a non-cured (flowable/liquid) potting compound 5 above the LED chip 4,

[0125] wherein the potting compound 5 contains at least one type of phosphor particles and preferably a matrix material,

[0126] wherein a predetermined potential is applied to at least one LED chip 4 directly or indirectly during the dispensing process.

[0127] By means of the further proposals for reducing or for avoiding such segregation as mentioned above and in the particularly preferred exemplary embodiments, LED modules having a more homogeneous phosphor particle distribution in comparison with the known LED modules can be provided, such that a more homogeneous light emission overall can be provided as a result. In particular, the present invention is not restricted to LED modules produced by a dam-and-fill method, but rather relates generally to all LED modules in which a potting compound is applied in which phosphor particles can still move within the matrix material (for example on an epoxy or silicone basis).

[0128] The present invention is not restricted to the exemplary embodiments above, as long as it is encompassed by the subject matter of the following claims Furthermore, the exemplary embodiments above can be combined with and among one another in any desired way. In particular, the present invention is not restricted to the case where all LED chips arranged in the light field must necessarily be provided with phosphor.