Method for measuring light radiation emitted by a plurality of light-emitting diodes and device for measuring light radiation emitted by a plurality of light-emitting diodes arranged side by side on a carrier

Abstract

Method for measuring light radiation (300) emitted by a plurality of light-emitting diodes (210), wherein the light radiation (300) from the light-emitting diodes (210) arranged side by side on a carrier (200) is measured in groups, wherein groups (220) to be measured are each measured from the light-emitting diodes (210) in a predetermined measuring position, and wherein in each group (220) to be measured the associated light-emitting diodes (210) successively emit the light radiation (300), wherein one end (121) of an optical fiber (120) which is connected to a measuring device (130) is irradiated through an optical device (140) with the light radiation (300) emitted by the light-emitting diode (210) of the group (220) to be measured, so that a part of the light radiation (300) is coupled into the optical fiber (120) and guided to the measuring device (130), wherein the optical device (140) causesthat the light radiation (300) passing through the optical device (140) is emitted in diffuse form, the optical device (140) comprising a diffuser, the light-emitting diodes (210) of the individual groups (220) being contacted by an activation device (110) used to activate the light-emitting diodes (210), which successively activates the light-emitting diodes (210) of a group (220), the activation device (110) comprising an arrangement of measuring needles (111) attached to a holder, via which the light-emitting diodes (210) are contacted at a front face, the measuring needles (111) extending laterally to the respective light-emitting diodes (210).

Description

[0001] The present invention relates to a method and a device for measuring light radiation emitted by a light-emitting diode.

[0002] Methods and devices for measuring light radiation emitted by a light-emitting diode are known from the documents US 2009 / 0 021 732 A1, US 2009 / 0 236 506 A1, US 2005 / 0 002 023 A1, DE 198 26 409 C2, JP 2000- 131 189 A and JP 2009- 150 791 A.

[0003] During the production of light-emitting diodes (LEDs), tests are typically conducted to measure the emitted light. Such light measurements are sometimes performed at the wafer level, i.e., at a stage of the process in which the LEDs are still located on a common carrier substrate (wafer).

[0004] In one known measuring method, the free end of an optical fiber is positioned at a relatively large distance above a wafer, and an LED located underneath is activated to emit light. Part of the light radiation is coupled into the optical fiber via the free end and then guided to a suitable measuring device. All LEDs are measured in groups. By positioning the wafer, groups of LEDs are arranged at a predetermined measuring position below the end of the optical fiber, and the LEDs in each group are activated one after the other. The use of the optical fiber means that the light output emitted by the LEDs is only measured over a relatively small angular range (typically around 1 sr).

[0005] After a wafer has been singulated into individual LED chips, the chips are further processed, in particular encapsulated in a potting material (e.g., silicone). The LED components produced in this way are then calibrated and measured in a hollow sphere with a diffusely reflecting interior (a so-called integrating sphere). This can result in relatively large deviations compared to measurements performed on a wafer. Depending on the component, these deviations can lead to yield losses and associated costs. One cause of these deviations is the different coupling of the light radiation, which can occur via the interface between the thin-film material of the LEDs (e.g., GaN) and air in measurements on a wafer, and via the interface between the thin-film material and the potting material in the finished component.

[0006] Another cause is the different emission behavior of LEDs, for example, due to a different internal layer structure and / or a different roughening or surface structuring on a light exit side intended for the purpose of light extraction. In conjunction with the small angular range covered by the optical fiber, this can lead to deviations or measurement errors in measurements performed at the wafer level. Further measurement distortions related to the small angular range are, for example, the result of the different positioning of LEDs in a group relative to the optical fiber, as well as different reflection and shadowing of the light radiation.

[0007] To solve such problems, in particular to avoid deviations due to different radiation characteristics, the so-called partial flux measurement can be performed, in which a larger proportion of the light radiation emitted by LEDs on a wafer is "collected". This can be achieved with the help of an integrating sphere, but this requires appropriate calibration. This is because the light radiation emitted by an LED is not only reflected many times within the sphere, but also many times by the wafer, which means that there is an influence that depends on the environment of the LED (wafer edge, dark fields such as alignment fields, etc.). To correct the quality, a time-consuming auxiliary light measurement can be performed for each LED, but this leads to a significant reduction in measurement throughput.

[0008] The object of the present invention is to provide an improved solution for measuring light radiation from a light-emitting diode.

[0009] This object is achieved by a method according to claim 1 and by a device according to claim 5. Further advantageous embodiments of the invention are specified in the dependent claims.

[0010] According to one aspect of the invention, a method for measuring light radiation emitted by a light-emitting diode is proposed. In the method, one end of an optical fiber is irradiated with the light radiation emitted by the light-emitting diode through an optical device. The optical fiber is connected to a measuring device. In this way, a portion of the light radiation is coupled into the optical fiber and guided to the measuring device. The optical device causes the light radiation passing through the optical device to be emitted in diffuse form toward the end of the optical fiber.

[0011] In contrast to the conventional procedure described above, according to which a free end of an optical fiber is directly irradiated with the light radiation emitted by a light-emitting diode, the method provides for the use of an optical device arranged between the light-emitting diode and the end of the optical fiber. The optical device thus arranged upstream of the optical fiber influences the light radiation passing through the optical device in such a way that the light radiation is diffusely emitted by the optical device. In other words, the light radiation emitted by the light-emitting diode is converted into diffuse light radiation with the aid of the optical device. The optical device, which can also be referred to as a "diffuser" or "diffuser device", can, for example, be designed such that the light radiation is (chaotically) deflected in different directions or diffusely scattered.

[0012] In this way, the optical device can ensure that the light radiation emitted by the light-emitting diode in a corresponding radiation or angular range is redistributed, in particular spatially homogenized, before the light radiation enters the optical fiber (via its end). For example, it is possible for the light radiation emerging from the optical device to essentially follow a Lambertian radiation distribution. It is also possible for the light radiation to follow a different radiation distribution. The redistribution has the effect that the portion of the radiation fed to the optical fiber can comprise components from a (significantly) larger angular range. This applies in comparison to the conventionally carried out direct irradiation of an optical fiber, according to which there is a restriction to a small angular range around 0° (approximately delta function).

[0013] Considering a wider angular range of radiation makes it possible to suppress or at least (largely) reduce the influence of different radiation behavior, making the measurement of light radiation or radiant power less sensitive and more accurate. In this way, for example, light-emitting diodes with different roughening or surface structuring can be directly compared with each other with a high degree of reliability, even at the wafer level. The measurement method can also be used to optimize such output coupling structures at the wafer level. A further advantage is that the method can be carried out using a test device previously used for light measurement, which is simply expanded to include the optical device.The use of an integrating sphere, which is associated with disadvantages such as complex integration and time-consuming auxiliary light measurements, can be eliminated. Furthermore, if effects such as backscattering or backreflection can be avoided or neglected, the measurement is independent of the environment of the LED in question.

[0014] Although this method cannot correct deviations that may occur between a LED measured at wafer level and the later encapsulated component (caused by different output efficiency), it does allow for an improved correlation between the measured radiant power or brightness of a "naked" LED and the radiant power of the later component.

[0015] The optical device has a diffusing screen or the optical device is designed in the form of such a diffusing screen. This can be a relatively simple and therefore cost-effective diffusing screen. The diffusing screen is designed to scatter the light emitted by the LED in different directions in order to emit the light radiation in diffuse form towards the end of the optical fiber. For this purpose, the diffusing screen can be designed, for example, with a diffusely scattering, roughened surface. A further embodiment is a base body with scattering particles or scattering centers located therein, and / or a base body with a first refractive index and smaller bodies with a second refractive index located therein.

[0016] In a further embodiment, the optical device has an anti-reflection coating. This configuration, which can be considered particularly for a microlens array, offers the possibility of suppressing back reflection of the light radiation to the light-emitting diode with high reliability.

[0017] In a further embodiment, the emitted light radiation, which impinges on the optical device and thereby passes through the optical device, is emitted from the light-emitting diode at an emission angle in the range of 160°. This makes it possible for the light radiation diffusely emitted by the optical device and thus fed to the optical fiber to include radiation components from (essentially) the entire emission range of the light-emitting diode.

[0018] This can be facilitated by positioning the optical device relatively close to the LED. Another embodiment in this regard provides for the optical device to be arranged at a distance of several millimeters from the LED. One possible distance is, for example, 3 mm.

[0019] To facilitate handling, the end of the optical fiber can be arranged at a relatively large distance from the LED (and thus from the optical device). In another embodiment, the end of the optical fiber is arranged at a distance in the range of several tens of millimeters from the LED. A possible distance could be, for example, 80 mm.

[0020] In a further embodiment, a collimation device is arranged in the region of the end of the optical fiber. In this way, the end of the optical fiber can be irradiated with the light radiation emitted by the light-emitting diode through the optical device and the collimation device. The collimation device can collect the light radiation emitted in diffuse form by the optical device over a relatively large angular range and transmit it to the end of the optical fiber. This makes it possible to provide a relatively large distance between the optical device and the light-emitting diode instead of a small distance, whereby radiation components from a large or essentially the entire emission range of the light-emitting diode can still be supplied to the optical fiber. Providing a large distance between the optical device and the light-emitting diode promotes easy handling.The distance can, for example, be in the range of 10mm to 30mm.

[0021] The light radiation is measured by light-emitting diodes arranged next to one another on a carrier. The measurement is carried out in groups, with each group of light-emitting diodes to be measured being measured in a predetermined measuring position. For each group to be measured, the associated light-emitting diodes emit light radiation one after the other. In the measuring position, the light-emitting diodes of the individual groups can be arranged directly below the end of the optical fiber. Furthermore, the light-emitting diodes of the individual groups are contacted by an activation device used to activate the light-emitting diodes, which activates the light-emitting diodes in a group one after the other. The light radiation emitted one after the other in this way can pass through the optical device in the manner described above and reach the optical fiber (via any collimation device provided).In contrast to the use of an integrating sphere, the LEDs arranged on the carrier can be measured with significantly higher throughput. The redistribution or homogenization of the light radiation achieved with the help of the optical device also makes it possible to suppress measurement deviations or errors, for example, caused by slightly different positions of LEDs in a group relative to the optical fiber, as well as different shadowing and reflection.

[0022] The carrier can be, for example, a common substrate disk or wafer equipped with the LEDs. The LEDs are (still) connected to each other via the wafer. Alternatively, it can also be another carrier. The carrier can be, for example, a separating film onto which a substrate equipped with LEDs is arranged for a separation process. In this sense, the LEDs measured in groups and arranged on the carrier can represent individual LEDs or LED chips.

[0023] According to a further aspect of the invention, a device for measuring light radiation emitted by a light-emitting diode is proposed. The device can be used to carry out the method described above or its various embodiments. The device has an activation device for activating the light-emitting diode to emit the light radiation, an optical fiber with a free end or end provided for coupling in radiation, a measuring device connected to the optical fiber, and an optical device. The end of the optical fiber can be irradiated with the light radiation emitted by the light-emitting diode through the optical device, so that a portion of the light radiation can be coupled into the optical fiber and guided to the measuring device. The optical device is designed to emit the light radiation passing through the optical device in diffuse form towards the end of the optical fiber.

[0024] The use of a diffusely radiating optical device offers the possibility of locally redistributing the light radiation emitted by the LED in front of the optical fiber, or of achieving a more uniform radiation distribution. This allows the portion of the light radiation coupled into the optical fiber to include radiation components from a wider angular range. This makes it possible, in particular, to suppress or reduce the influence of different emission behaviors of LEDs, thus making the light measurement less sensitive.

[0025] In one embodiment, the device comprises a collimation device arranged in the region of the end of the optical fiber, so that the end of the optical fiber can be irradiated with the light radiation emitted by the LED through the optical device and additionally through the collimation device. In such a configuration, the optical device can be arranged at a relatively large distance from the LED to be measured.

[0026] The device is designed for measuring light-emitting diodes arranged next to one another in groups on a carrier (for example a wafer or separating film). The device has a holding device with the aid of which the carrier with the light-emitting diodes can be held. The carrier can also be positioned via the holding device such that a group of light-emitting diodes to be measured is arranged in a predetermined measuring position. The holding device can, for example, be designed in the form of a wafer chuck or comprise such a wafer chuck. The activation device of the device is designed to activate the light-emitting diodes of a group of light-emitting diodes to be measured and arranged in a measuring position one after the other to emit light radiation. The activation device comprises an arrangement of measuring needles fastened to a holder, via which light-emitting diodes are contacted on a front side.

[0027] The advantageous embodiments and further developments of the invention explained above and / or reproduced in the subclaims can - except, for example, in cases of clear dependencies or incompatible alternatives - be used individually or in any combination with one another.

[0028] The above-described properties, features, and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more readily understood in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the schematic drawings. They show: Fig. 1 a device for measuring light radiation emitted by light-emitting diodes, the device comprising a diffuser device for redistributing the light radiation; Fig. 2 shows a plan view of a section of an arrangement of light-emitting diodes, wherein a group of light-emitting diodes to be measured is contacted by means of measuring needles of an activation device; Fig. 3 a side view of a microlens arrangement which can be used to redistribute light radiation; Fig. 4 measurement curves based on measurements of different LEDs with and without the use of a diffuser device; and Fig. 5 a further device for measuring light radiation emitted by light-emitting diodes, which has an additional collimation device.

[0029] Based on the following figures, embodiments of a measuring method and an associated measuring device 100 are described, with the aid of which light measurements on light-emitting diodes 210, for example, radiant power and luminous flux measurements, can be performed with high throughput. In particular, it is possible to cancel out or reduce the influence of different radiation or directional characteristics of light-emitting diodes 210, thereby allowing the measurements to be performed with greater accuracy.

[0030] Fig. Figure 1 shows a schematic representation of an embodiment of a device 100, with the aid of which light-emitting diodes 210 arranged next to one another on a carrier 200 can be measured. The device 100, which can also be referred to as a "prober" or "cluster prober," is designed for group-wise measurement, i.e., groups 220 of light-emitting diodes 210 can be subjected to a light measurement in a predetermined measuring position (cf. Fig. 2).

[0031] The carrier 200 can be, for example, a substrate disk or a wafer 200, with the LEDs 210 arranged on a front side of the wafer 200. The LEDs 210 are (still) connected to one another via the wafer 200. In this respect, the device 100 can be used to perform light measurements at the wafer level, i.e., at a stage before the wafer 200 is singulated into separate LED chips.

[0032] As in Fig. As shown in Figure 1, the device 100 comprises a holding device 160 on which the wafer 200 can be arranged and held. The wafer 200 can be moved into a position intended for a light measurement via the holding device 160. In this way, a group 220 of light-emitting diodes 210 can be brought into the predetermined measurement position. The top view of Fig. 2, in which the front side of the wafer 200 is shown in detail, illustrates this by means of a dashed light diode group 220. As in Fig. As shown in Figure 2, such a group 220 can have several (in this case, for example, six) LEDs 210 arranged next to one another in a line. After measuring a group 220 of LEDs, the wafer 200 can be moved or shifted with the aid of the holding device 160, whereby another (in particular adjacent) group 220 can be brought into the measuring position and measured. To measure all LEDs 210 of the wafer 200, this process is repeated many times. For such a mode of operation, the holding device 160 can be designed, in particular, in the form of a movable wafer chuck or can comprise such a wafer chuck.

[0033] As in Fig. As indicated in Figure 1, the device 100 further comprises an activation device 110, with the aid of which light-emitting diodes 210 can be contacted and activated by applying current to emit a light radiation 300. The activation device 110 is designed to successively activate light-emitting diodes 210 of a group 220 brought into the measuring position to emit a light radiation 300.

[0034] For the light-emitting diodes 210 that can be measured with the device 100, it can be provided that the light-emitting diodes 210 can be contacted from both a front side and a rear side. With respect to the rear side, contacting can be effected via the holding device 160 or via a connection structure provided here, which contacts the wafer 200 on a rear side opposite the front side. For front-side contacting, the activation device 110 has, as shown in Fig. 2 shows a plurality of measuring needles 111 provided for contacting front-side contacts of the LEDs 210, which are arranged on a circular ring-shaped holder 112. The arrangement of holder 112 and measuring needles 111 can, for example, be comprised of a so-called "needle card" or "needle spider." According to the number of LEDs 210 in a group 220, six measuring needles 111 are provided in the illustrated embodiment. With the aid of the measuring needles 111, the LEDs 210 of a group 220 brought into the measuring position can be contacted separately and energized one after the other to emit a light radiation 300. The measuring needles 111 extend from the side to the respective LEDs 210 in order to impair a light measurement, in which the LEDs 210 emit a light radiation 300 via the front (or a light exit surface present here), as little as possible.

[0035] The device 100 further comprises, as in Fig. 1, an optical fiber 120 and a measuring device 130 connected to or coupled to the optical fiber 120. The optical fiber 120 can be designed, for example, in the form of a glass fiber. A design in the form of a light-conducting plastic fiber is also possible. The measuring device 130, with the aid of which the light radiation 300 emitted successively by the light-emitting diodes 210 of a group 220 is detected, can comprise, for example, a spectrometer, in particular a grating spectrometer. The measuring device 130 can be designed, in particular, for radiant power and luminous flux measurements.

[0036] The optical fiber 120 has a free end 121 arranged at a distance D1 above the wafer 200 (or its front side), via which a (small) part of the light radiation 300 of a light-emitting diode 210 can be coupled into the optical fiber 120. The light radiation 300 coupled in this way can be guided further via the optical fiber 120 to the measuring device 130. For the light measurement, a light-emitting diode group 220, which has been brought into the measuring position, is located directly below the end 121 of the optical fiber 120, as shown in Fig. 1 is indicated.

[0037] Instead of directly irradiating the free end 121 of the optical fiber 120 opposite the wafer 200 with the light radiation 300 emitted successively by light-emitting diodes 210, the irradiation of the end 121 in the device 100 takes place as in Fig. 1, the optical device 140 is arranged between the wafer 200 and the end 121 of the optical fiber 120, and is located at a distance D2 smaller than the distance D1, for example, relatively close to the wafer 200.

[0038] The optical device 140, which is referred to below as the diffuser device 140, can be designed in the form of a flat, planar body. Deviating from the schematic representation in Fig. 1, the diffuser device 140 can have smaller lateral dimensions than the wafer 200. During a light measurement, the diffuser device 140 is irradiated with the light radiation 300 at an entrance side 141 opposite the wafer 200, and the transmitted light radiation 300 can leave the diffuser device 140 at an opposite exit side 142 opposite the end 121 of the optical fiber 120. It is possible for the diffuser device 140 to be integrated, for example, into the probe card carrying the measuring needles 111, and for example, to be arranged on the holder 112 or attached thereto.

[0039] The diffuser device 140 arranged upstream of the optical fiber 120 is designed to influence the passing light radiation 300 such that the light radiation 300 is emitted in a diffuse form in the direction of the optical fiber 120. This can be achieved by (chaotic) deflection of the light radiation 300 in different directions and / or diffuse scattering. As explained in more detail below, the diffuser device 140 can be designed for this purpose, for example, in the form of a diffusing disk or in the form of a microlens array (see FIG. Fig. 3) are present.

[0040] The use of the diffuser device 140 makes it possible to capture the light radiation 300 emitted by a light-emitting diode 210 in a radiation or angular range and to redistribute it relatively evenly before the light radiation 300 (or a part thereof) reaches the optical fiber 120 and can be guided from there to the measuring device 130. The radiation range of a light-emitting diode 210 is in Fig. 1 based on a lateral radiation angle A2 relative to a surface normal of the wafer 200. Preferably, the optical device 140 effects the most spatial homogenization of the light radiation 300 possible. In this case, the radiation 300 emitted by the diffuser device 140 can essentially follow a Lambertian radiation distribution, or another radiation distribution.

[0041] This mode of operation makes it possible for the portion of the light radiation 300 or the far field supplied to the optical fiber 120 and thus to the measuring device 130 to encompass portions of a relatively large angular range of the light radiation 300 emitted by a light-emitting diode 210, in particular, substantially the entire emission range of a light-emitting diode 210. This can be facilitated by positioning the diffuser device 140 relatively close to the wafer 200. The detectable angular range is significantly larger than with direct irradiation of the optical fiber 120 (with an angular range around 0°).

[0042] A possible maximum detectable angular range of the radiation 300 is explained in more detail below using an exemplary geometric consideration. For the optical fiber 120, for example, a numerical aperture NA of approximately 0.22 can be assumed. This results in A1=sin−1NA a half aperture angle A1 of the optical fiber 120 of about 13°, as in Fig. 1 is indicated.

[0043] For handling reasons, the optical fiber 120 or its end 121 can be arranged at a distance of, for example, several tens of millimeters (or even more) from the wafer 200. In this case, a distance D1 in the range of 80 mm is assumed. The diffuser device 140 or its entrance side 141 can be arranged relatively close, for example, in the range of several millimeters, to the wafer 200. In this case, a distance D2 of 3 mm is assumed.

[0044] A half irradiation area B (field of view) on the diffuser device 140 is linked to the other quantities in the following way: B=(sinA1 / cosA1)*(D1−D2)∼18mm This results in the lateral or half beam angle A2 according to A2=tan−1(B / D2)∼80°.

[0045] The diffuser device 140 can thus capture that portion of the light radiation 300 originating from a light-emitting diode 210 which is emitted by the light-emitting diode 210 with a radiation angle in the range of 160° (2*A2). In this case, (essentially) the entire radiation range of the light-emitting diode 210 can be captured.

[0046] The detection of light radiation 300 from a large emission or angular range achievable with the aid of the diffuser device 140 offers a number of advantages. In particular, the influence of different emission profiles or directional characteristics of light-emitting diodes 210 can be suppressed or at least reduced. In this way, light-emitting diodes 210 with different emission behavior, wherein the light-emitting diodes 210 are arranged, for example, on different carriers or wafers 200 to be measured, can be compared with one another. Different emission behavior can result, in particular, from different roughening or surface structuring of the light exit side of the light-emitting diodes 210. Such structures, which can be produced, for example, by etching or a lithographic structuring process, serve to efficiently couple the light radiation 300 from the light-emitting diodes 210.

[0047] In the same way, the device 100 equipped with the diffuser device 140 can be used, for example, to reliably test the efficiency of such coupling-out structures on light-emitting diodes 210 of a carrier or wafer 200 as part of an optimization process. With direct irradiation of the optical fiber 120, this is not possible or only possible to a limited extent due to the comparatively small detectable angular range, or only an inadequate statement can be made about the efficiency of an output structure.

[0048] The redistribution or homogenization of the light radiation 300 further offers the possibility of achieving an improved correlation between the measured radiant power or brightness of a "bare" light-emitting diode 210 and the radiant power of the subsequent LED component. The device 100 also allows measurements to be performed with a relatively high throughput. This is because complex calibration measurements on individual light-emitting diodes 210, such as those required when using an integrating sphere, can be eliminated.

[0049] A light measurement carried out with the device 100 can be substantially independent of the environment of a measured light-emitting diode 210 or group 220, which is particularly the case with negligible backscattering or backreflection of the light radiation 300 at the diffuser device 140. However, even if such or other effects, as described below, occur, any influence on a light measurement resulting from this can be suppressed or reduced via the redistribution of the radiation 300 achievable with the aid of the diffuser device 140.

[0050] The LEDs 210 of a group 220 located in the measuring position, for example, each have a slightly different position relative to the optical fiber 120 arranged stationary relative to the group 220. Furthermore, the measuring needles 111 can cause different shadowing and light reflection when LEDs 210 of a group 220 are activated one after the other. Such effects can lead to falsified light measurements when the optical fiber 120 is directly irradiated. For example, a measurement image obtained without the use of the diffuser device 140, which depicts the radiant power of all LEDs 210 of the wafer 200, can exhibit striped measurement artifacts. This can result from measurement errors that can occur when measuring LEDs 210 at the edge of a measurement group 220. The influence of such effects can be prevented or reduced by the diffuser device 140.

[0051] A further advantage is that the diffuser device 140 can be integrated relatively easily into previously used measuring equipment. In this respect, the device 100 shown can, for example, be a conventional measuring device equipped with the diffuser device 140 (e.g., one designed to be replaceable). The diffuser device 140 can, for example, be arranged on the probe card, as already stated above.

[0052] The diffuser device 140 can, for example, be a diffusing disk 140, which can cause diffuse scattering of the light radiation 300. This can be a relatively simple and therefore cost-effective diffusing disk 140. The diffusing disk 140 can comprise a material transparent to the light radiation 300, in particular glass material, and, for example, have a roughened surface on the entrance side 141 and / or the exit side 142 to cause the scattering. In a further embodiment, the diffusing disk 140 can comprise a transparent base body with scattering particles or scattering centers located therein. A base body with a first refractive index, in which smaller bodies or scattering bodies with a second refractive index different from the first refractive index are arranged, is also possible.

[0053] Fig. 3 shows a detail of another possible embodiment of a diffuser device 140 usable in the device 100, which is designed in the form of a microlens arrangement 145 (also referred to as a "microlens array"). The microlens arrangement 145, which comprises a material transparent to the light radiation 300, in particular glass material, is in the form of a flat body, on whose exit side 142 a plurality of convex microlenses 147 are arranged. In this way, the light radiation 300 can be deflected or scattered in different directions before the light radiation 300 (or a portion thereof) reaches the optical fiber 120. Compared to a diffusion screen, the influence of backscattering, and thus reflection properties in the vicinity of a light-emitting diode 210, can be largely avoided.

[0054] The microlenses 147 of the microlens array 145 are significantly smaller in lateral dimensions than the LEDs 210 to be measured. This can promote a relatively uniform redistribution of the light radiation 300, for example, achieving a Lambertian radiation distribution. In this respect, the microlenses 147 can be arranged in a grid with a pitch in the range of 1 to 100 micrometers, for example, 25 micrometers. The pitch depends on the lateral size of the LEDs 210 and the distance of the microlens array 145 from the LEDs 210 or the wafer 200.

[0055] The microlens array 145 further preferably comprises an anti-reflection layer 150, which as in Fig. 3, in particular, it can be formed on both sides, i.e., both on the (here flat) entrance side 141 and on the light exit side 142. The anti-reflection layer 150, which has a thickness adapted to the wavelengths of the light radiation 300 of the measured LEDs 210, makes it possible to suppress back-reflection of the light radiation 300 to a measured LED 210 with a high degree of reliability. In this way, the light measurement can be carried out relatively accurately and, in particular, independently of the environment of the LED 210. Instead of a double-sided design, the anti-reflection layer 150 can also be provided on only one of the two sides 141, 142.

[0056] In addition to the Fig. Other configurations of a microlens array are also possible for the microlens array 145 shown in Figure 3. For example, microlenses 147 can be present on the entrance side 141, whereas the exit side 142 is flat, which can be achieved, for example, by using the microlens array 145 shown in reverse. A configuration is also possible in which microlenses 147 are present on both the entrance side 141 and the exit side 142. Furthermore, it is conceivable that concave microlenses (on one or both sides) are provided instead of the convex microlenses 147 shown. For such configurations, the above-mentioned details (e.g., pitch size, anti-reflection layer on one or both sides) can apply analogously.

[0057] To illustrate the positive effect that can be achieved by using an optical diffuser device, Fig. Four measurement curves based on light measurements of three different LEDs with and without a diffuser device. The diffuser device was arranged between the LEDs and an optical fiber used in the measurement. A relatively simple diffuser plate with a curved contour was used as the diffuser device. The three measured LEDs had differently shaped surfaces or, respectively, the decoupling structures provided for them.

[0058] Shown in each case is a relative deviation R from an ideal Lambertian radiator as a function of a radiation angle W. The angle W refers to a surface normal of the LEDs and thus to a main radiation direction. The "course" of the Lambertian radiator is shown in Fig. 4 is indicated by a line running constant at R = 1. For the measurement, the optical fiber was moved in a semicircle around the diodes to measure the light radiation emitted at different angles W.

[0059] The measurement curves 310, 320, and 330 are based on measurements without the diffuser device, and the measurement curves 311, 321, and 331 are based on measurements using this device. The measurement curves 310 and 311 refer to a first diode, the measurement curves 320 and 321 to a second diode, and the measurement curves 330 and 331 to a third diode. In particular, the measurement curves 320 and 330 obtained without the diffuser device deviate relatively strongly from the Lambertian radiator. With the use of the diffuser device, the deviation R becomes (significantly) smaller, as can be seen from the measurement curves 321 and 331. The curved shape of the measurement curves 311, 321, and 331 is due to the curved shape of the diffuser device used.

[0060] Fig. Fig. 5 shows a schematic representation of a device 100 according to a further embodiment, which essentially has the same structure and the same functioning as the device 100 of Fig. 1. It is pointed out that with regard to details already described, which relate to similar or identical components and features, possible advantages, etc., reference is made to the above explanations.

[0061] The device 100 of Fig. 5 additionally includes a collimation device 190 arranged in the region of the end 121 of the optical fiber 120. The collimation device 190 is arranged at a relatively short distance from the end 121 of the optical fiber 120 or is connected to it. In this way, the end 121 of the optical fiber 120 is irradiated through the diffuser device 140 and additionally through the collimation device 190.

[0062] The collimation device 190, which is arranged at a distance from the diffuser device 140, can detect the light radiation 300 emitted by the diffuser device 140 in a relatively large angular range and can be forwarded or collimated to the end 121 of the optical fiber 120. The collimation device 190 can, for example, comprise one or more lenses. The angular range that can be detected by the collimation device 190 is Fig. 5 using a (half) aperture angle A3. The aperture angle A3 of the collimation device 190 is (significantly) larger than that shown in Fig. 1 indicated opening angle A1 of the optical fiber 120.

[0063] The use of the collimation device 190 makes it possible to select a relatively large distance D2 between the diffuser device 140 and the wafer 200, thereby achieving easier handling. The distance D2 can be larger than in the Fig. 1. For example, the distance D2 can be in the range between 10 mm and 30 mm.

[0064] The presence of a larger distance D2 leads to a larger (half) irradiation area B on the diffuser device 140 used for radiation homogenization. This is the case if the diffuser device 140 is arranged as in Fig. 5 is again irradiated with light radiation 300 of the (essentially) entire radiation area (radiation angle A2) of a light-emitting diode 210. In this context, it may be considered to design the diffuser device 140 in relation to the embodiment of Fig. 1 with larger lateral dimensions. Due to the use of the collimation device 190 with the available large aperture angle A3, light radiation 300 from the larger irradiation area B can be captured and coupled into the end 121 of the optical fiber 120.

[0065] The embodiments explained with reference to the figures represent preferred or exemplary embodiments of the invention for measuring light radiation or radiant power of light-emitting diodes. In addition to the described and illustrated embodiments, further embodiments are conceivable, which may include further modifications and / or combinations of features.

[0066] In particular, the materials and numerical values ​​specified above may be replaced by other information. This applies, for example, to the Fig. 1, or information on the distances D1, D2, the angles A1, A2, the irradiation area B, etc. For example, the pitch of a microlens array can also have a different size. Furthermore, a device 100 can be configured such that a group 220, which is measured in a measuring position, comprises a different number of LEDs 210. In this regard, a probe card can also comprise a different number of measuring probes 111.

[0067] The distance D1 between the end 121 of an optical fiber 120 and a measured light-emitting diode 210 (or an associated carrier 200) can, for example, be in a range from 50 mm to 200 mm. A possible distance D1 is, as stated above, for example, 80 mm, or also, for example, 100 mm. The distance D2 between a diffuser device 140 and a light-emitting diode 210 (or a carrier 200) can, for example, be in a range from 2 mm to 30 mm. A possible distance D2 is, as stated above, for example, 3 mm, or also, for example, 5 mm. When using a collimation device 190, the distance D2 can be greater. Furthermore, a diffuser device 140 can be irradiated with light radiation 300 emitted by a light-emitting diode 210 at an angle in a range of, for example, 40° to 170°.

[0068] The method or an associated device 100 (as well as modifications thereof) can further be used to measure light-emitting diodes 210 arranged on a carrier 200 other than a wafer. For example, this can be a separating film 200 used in the singulation of light-emitting diodes 210. The light-emitting diodes 210 that can be measured with the device 100 and arranged on the separating film 200 can therefore represent (already) singulated light-emitting diodes 210 or LED chips. The above explanations can be applied analogously to a separating film 200 with light-emitting diodes 210.

[0069] Furthermore, a device 100 can also be used for measuring the light of light-emitting diodes 210, which, contrary to the above description, can only be contacted via the front side. In this case, the light-emitting diodes 210 can each have two front-side contacts. This can apply, for example, to light-emitting diodes 210 that are measured arranged on a separating film 200. To contact such light-emitting diodes 210, an activation device 110 with a probe card comprising measuring needles 111 can be used in the same way. An light-emitting diode 210 can be contacted on the front side by two measuring needles 111 or by "double needles."

[0070] With regard to a diffuser device 140, it is conceivable that this could be used instead of the Fig. 1 and Fig.5 has a curved shape. It is also possible for a diffuser device 140 in the form of a scattering disc to be formed (on one or both sides) with an anti-reflection coating 150.

[0071] Furthermore, attention is drawn to the possibility that a light radiation diffusely emitted by a diffuser device 140 and thus redistributed can also follow a different radiation distribution instead of a Lambertian radiation distribution in order to suppress or at least reduce differences in the radiation profile of light-emitting diodes. List of reference symbols 100 device 110 Activation device 111 Measuring needle 112 bracket 120 optical fibers 121 End 130 measuring device 140 Diffuser device 141 Entrance side 142 Exit side 145 microlens array 147 Microlens 150 anti-reflective coating 160 holding device 190 Collimation device 200 wafers / release film 210 LED 220 Group 300 light radiation 310, 311 measurement curve 320, 321 measurement curve 330, 331 measurement curve A1 Opening angle A2 Beam angle A3 opening angle B Irradiation area D1 distance D2 distance R Relative deviation W angle

Claims

[1] Method for measuring a light radiation (300) emitted by a plurality of light-emitting diodes (210), wherein the light radiation (300) is measured in groups by the light-emitting diodes (210) arranged next to one another on a carrier (200), wherein groups (220) of the light-emitting diodes (210) to be measured are each measured in a predetermined measuring position, and wherein for each group (220) to be measured, the associated light-emitting diodes (210) successively emit the light radiation (300), wherein one end (121) of an optical fiber (120), which is connected to a measuring device (130), is irradiated through an optical device (140) with the light radiation (300) emitted by the light-emitting diode (210) of the group (220) to be measured, so that a part of the light radiation (300) is coupled into the optical fiber (120) and fed to the measuring device (130), wherein the optical device (140) causesthat the light radiation (300) passing through the optical device (140) is emitted in diffuse form, wherein the optical device (140) has a diffusion screen, wherein the light-emitting diodes (210) of the individual groups (220) are contacted by an activation device (110) used to activate the light-emitting diodes (210), which activates the light-emitting diodes (210) of a group (220) successively, wherein the activation device (110) comprises an arrangement of measuring needles (111) fastened to a holder, via which the light-emitting diodes (210) are contacted on a front side, wherein the measuring needles (111) extend from the side to the respective light-emitting diodes (210). [2] Method according to the preceding claim, wherein the optical device (140) comprises an anti-reflection layer (150). [3] Method according to one of the preceding claims, wherein the light radiation (300) passing through the optical device (140) is emitted by the light-emitting diode (210) with a radiation angle in the range of 160°. [4] Method according to one of the preceding claims, wherein the optical device (140) is arranged at a distance (D2) of several millimeters from the light-emitting diode (210), and wherein the end (121) of the optical fiber (120) is arranged at a distance (D1) in a range of several tens of millimeters from the light-emitting diode (210). [5] Device (100) for measuring a light radiation (300) emitted by a plurality of light-emitting diodes (210) arranged next to one another on a carrier (200), comprising an activation device (110) for activating a group (220) of the light-emitting diodes (210) in groups to emit the light radiation (300), an optical fiber (120) with an end (121), a measuring device (130) connected to the optical fiber (120), and an optical device (140), wherein the end (121) of the optical fiber (120) can be irradiated through the optical device (140) with the light radiation (300) emitted by the light-emitting diode (210), so that a part of the light radiation (300) can be coupled into the optical fiber (120) and guided to the measuring device (130), and wherein the optical device (140) is designed to Device (140) for emitting passing light radiation (300) in diffuse form (120),wherein the optical device (140) has a diffusing screen, wherein the light-emitting diodes (210) of the individual groups (220) are contacted by the activation device (110), which activates the light-emitting diodes (210) of a group (220) successively, wherein the activation device (110) comprises an arrangement of measuring needles (111) fastened to a holder, via which the light-emitting diodes (210) can be contacted on a front side, wherein the measuring needles (111) extend from the side to the respective light-emitting diodes (210). [6] The device of claim 5, wherein the optical device (140) comprises an anti-reflection layer (150). [7] Device according to one of claims 5 or 6, further comprising a collimation device (190) arranged in the region of the end (121) of the optical fiber (120). [8] Device according to one of claims 5 to 7, designed for measuring light-emitting diodes (210) arranged next to one another on a carrier (200) in groups, wherein the device has a holding device (160) for holding the carrier (200) with the light-emitting diodes (210) and for arranging groups (220) of light-emitting diodes (210) to be measured in a predetermined measuring position.

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