METHOD OF MANUFACTURING A LIGHT CONVERTING DEVICE

Abstract

In a method of manufacturing light converting devices each in form of a converter element attached on a carrier substrate, a carrier wafer and a converter wafer with lateral dimensions larger than the lateral dimensions of the converter elements are provided. A bond layer is applied to one of the carrier wafer and the converter wafer, and the converter wafer is securely fixed on the carrier wafer via the bond layer, thereby forming a wafer stack. The wafer stack is then separated into pieces such that first of said pieces have the lateral dimensions of the converter elements and do not share any edge with an edge of the wafer stack, said first pieces forming the light converting devices. With this method, a light converting device without any squeezed out bonding material, e.g. glue, is achieved.

Claims

1. A method of manufacturing light converting devices each being formed of a converter element attached on a carrier substrate, said converter element converting light of a first wavelength region into light of a second wavelength region, the method comprising: providing a carrier wafer and a converter wafer with lateral dimensions larger than lateral dimensions of the converter elements, applying a bond layer to one of the carrier wafer and the converter wafer and securely fixing the converter wafer on the carrier wafer via the bond layer, thereby forming a wafer stack, separating the wafer stack into pieces such that first of said pieces have the lateral dimensions of the converter elements and do not share any edge with an edge of the wafer stack, said first pieces forming the light converting devices.

2. The method according to claim 1, wherein the carrier wafer and the converter wafer are provided with lateral dimensions allowing to manufacture several of the light converting devices from the carrier wafer and the converter wafer.

3. The method according to claim 1, wherein said carrier wafer is formed of a metallic material and comprises a layer or layer sequence forming a mirror on its surface.

4. The method according to claim 1, wherein said bond layer is formed of a glue.

5. The method according to claim 4, wherein said glue is pressed to a thickness of <3 m between the converter wafer and the carrier wafer.

6. The method according to claim 1, wherein the separation of the wafer stack into pieces is performed such that the converter elements have a rectangular shape with edge lengths of <1 mm.

7. The method according to claim 1, wherein said converter wafer is provided with a thickness of <70 m.

8. The method according to claim 1, wherein said converter wafer is provided of a luminescent ceramics.

9. The method according to claim 1, wherein the separation of the wafer stack into pieces is performed as a two-step process in which a first one of the converter wafer and carrier wafer is cut with first cutting parameters adapted to a material of this first wafer, and then a second one of the converter wafer and carrier wafer is cut with second cutting parameters adapted to a material of this second wafer.

10. The light converting device being manufactured by the manufacturing method according to claim 1, and the light converting device being formed of the converter element bonded by the bond layer on the carrier substrate, said converter element converting the light of the first wavelength region into the light of the second wavelength region, wherein the lateral dimensions of the converter element coincide with lateral dimensions of the carrier substrate, said converter element being accurately fitted to said carrier substrate, and wherein there is no material of the bond layer squeezed-out at side faces of the light converting device.

11. The light converting device according to claim 10, wherein said carrier substrate is formed of a metallic material and comprises a layer or layer sequence forming a mirror on its surface.

12. The light converting device according to claim 10, wherein said converter element has a rectangular shape with edge lengths of <1 mm and a thickness of <70 m.

13. A light source for white light comprising one or several lasers or laser diodes and at least one light converting device according to claim 10, wherein said light converting device is arranged to convert part of the light of said one or several lasers or laser diodes into converted light of another wavelength region, said light of said one or several lasers or laser diodes not converted summing up with said converted light to form white light.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0013] The proposed method is described in the following by way of examples in connection with the accompanying figures. The figures show:

[0014] FIG. 1 a schematic view of a light converting device according to the prior art;

[0015] FIG. 2 a schematic view of a first phase of the proposed method; and

[0016] FIG. 3 a schematic view of several light converting devices according to the present invention after performing the final step of the proposed method.

DESCRIPTION OF EMBODIMENTS

[0017] The problems arising with the method of manufacturing a light converting device according to the prior art have already been explained in connection with FIG. 1 in the introductory portion of this description. The proposed method avoiding the drawbacks of the prior art is described in the following in an exemplary embodiment in which the converter element is attached to a carrier substrate having a mirror at the surface.

[0018] According to this example a carrier wafer (substrate) 7 and a converter wafer 6 are provided with lateral dimensions substantially larger than the lateral dimensions of the light converting devices to be manufactured. The lateral dimensions are e.g. the diameter in case of a circular wafer or the edge lengths in case of a rectangular wafer. The converter wafer 6 in this example is quadratic and has a diameter sufficiently large to allow for singulation of 55, i.e., 25, individual converter elements. The carrier wafer carries a layer or layer sequence forming a mirror 3 on top as can be seen from FIG. 2. The mirror can be formed of a metallic layer, of a dielectric layer or layer sequence, or of a combination of a metallic layer and a dielectric layer sequence. The bulk of the carrier wafer preferably consists of a metal or a ceramic material with good heat conductivity. A glue 4 is applied to the surface of the carrier wafer 7 in order to securely attach the converter wafer 6 to the carrier wafer 7. Due to the substantially larger lateral dimensions of the two wafers compared with the lateral dimensions of the light converting devices to be manufactured the maximum glue volume to be applied is not restricted by the size requirement of an individual converter element anymore. Therefore, glue volumes substantially larger than 1 nl can be applied for which different techniques can be used. FIG. 2 shows the glue 4 applied to the surface of the carrier wafer 7. After application of the glue 4 the converter wafer 6 is pressed against the carrier wafer 7 in order to achieve a thickness of the resulting glue layer of only a few m or less, preferably <3 m, more preferably <1 m, over the full surface of the carrier wafer 7.

[0019] After final curing of the glue 4, the resulting wafer stack is separated into several pieces, e.g. using a dicing process. This separation or dicing step is performed such that several pieces corresponding to the to be manufactured light converting devices and having the dimensions of these devices are cut out of the wafer stack such that these light converting devices do not share any edge with the edges of the wafer stack. This is shown in FIG. 3 indicating different light converting devices 8 after separation of the wafer stack. The pieces 9 at the edges of the wafer stack are discarded. Only these edge pieces 9 show a squeezing-out of the glue 4. The manufactured light converting devices 8, however, do not show any squeeze-out material and do thus not have the problems of the light converting devices manufactured according to the prior art.

[0020] While the invention has been illustrated and described in detail in the drawings and forgoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. The proposed processing on wafer level can also be combined with other bonding techniques such as e.g. soldering. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from a study of the drawings, the disclosure, and the appended claims. Thus, e.g., the invention might not only be applied to light converting devices to be used together with laser-based light sources but also for light converting devices for other light sources such as e.g. light emitting diodes (LEDs).

[0021] In the claims, the word comprising does not exclude other elements or steps and the indefinite articles a or an do not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention.

LIST OF REFERENCE SIGNS

[0022] 1 converter element [0023] 2 carrier substrate [0024] 3 mirror/mirror layer [0025] 4 glue [0026] 5 blue light [0027] 6 converter wafer [0028] 7 carrier wafer [0029] 8 light converting device [0030] 9 edge pieces