Method and device for laser-based machining of flat substrates
A method for laser-based machining of a flat substrate, to separate the substrate into a plurality of sections, in which the laser beam of a laser is directed at the substrate using an optical arrangement, which is positioned in the beam path of the laser. The optical arrangement forms a laser beam focal line that is extended as viewed along the beam direction and the substrate is positioned relative to the laser beam focal line such that an induced absorption is produced in the material of the substrate along a section of the laser beam focal line that is extended as viewed in the beam direction.
1. A system comprising:
a substrate; and
a device for laser-based machining that is configured to separate the substrate into a plurality of pieces, the device comprising:
a laser providing a laser beam for machining the substrate when directed at the substrate, the wavelength λ of the laser beam being such that a material of the substrate is transparent to the wavelength λ; and
an optical arrangement positioned in a beam path of the laser, wherein:
the optical arrangement comprises a first optical element and a second optical element;
the second optical element is disposed on the beam output side of the first optical element, at a distance z 1 from the first optical element; and
the first optical element and the second optical element are positioned and directed such that the laser beam strikes the second optical element in a ring shape, and a laser beam focal line extending along the direction of the laser beam is generated on the beam output side of the second optical element at a spacing z 2 from the second optical element; wherein:
the substrate is positioned relative to the laser beam focal line so that in the material of the substrate, an induced absorption takes place along a segment of the laser beam focal line that is extended as viewed in the direction of the beam along a single continuous cracking zone, wherein an induced crack formation is produced in the material of the substrate along the said extended segment.
2. The system of claim 1 , wherein the second optical element comprises a focusing optical element with spherical aberration.
3. The system of claim 1 , wherein the first optical element comprises a nonspherical free surface, which is shaped to form the laser beam focal line with a defined length l.
4. The system of claim 1 , wherein the device for laser based machining further comprises a third optical element positioned in the beam path of the laser between the first and the second optical element.
5. The system of claim 1 , wherein the first optical element comprises a conical prism or axicon.
6. The system of claim 1 , wherein:
the first optical element comprises a diaphragm and the second optical element comprises a focusing element; and
the diaphragm is positioned to block beam bundles in a center of the laser beam incident on the diaphragm without blocking edge beams of the laser beam.
7. The system of claim 6 , wherein the diaphragm is an annular diaphragm.
8. The system of claim 2 , wherein the first optical element comprises a diaphragm disposed in the beam path of the laser beam in front of the second optical element, wherein the diaphragm is positioned to block beam bundles in a center of the laser beam incident on the diaphragm without blocking edge beams of the laser beam.
9. The system of claim 8 , wherein the diaphragm is an annular diaphragm.
10. The system of claim 2 , wherein the second optical element comprising the focusing optical element with spherical aberration comprises at least one convex surface.
11. The system of claim 1 wherein the second optical element comprises a lens with a convex surface.
12. The system of claim 4 , wherein the third optical element comprises a collimation lens.
13. The system of claim 12 , wherein the third optical element comprises a convex surface.
14. The system of claim 1 , wherein the substrate comprises two opposite substrate surfaces and is positioned in relation to the laser beam focal line such that the extended segment of the induced absorption in the material of the substrate extends up to at least one of the two opposite substrate surfaces, and
the average laser power, measured directly on the output side of the laser beam, is between 10 watts and 100 watts.
15. The system of claim 14 , wherein the substrate is positioned within the device in relation to the laser beam focal line such that the extended segment of the induced absorption in the material of the substrate extends starting from one of the two opposite substrate surfaces into the substrate, but not up to the other of the two opposite substrate surfaces.
16. The system of claim 15 , the substrate is positioned in relation to the laser beam focal line such that the extended segment of the induced absorption in the material of the substrate extends starting from one of the two opposite substrate surfaces into the substrate over 80% of the thickness of the substrate, but not up to the other of the two opposite substrate surfaces.
17. The system of claim 1 , wherein the length l of the laser beam focal line in the longitudinal direction of the beam is between 0.1 mm and 100 mm.
18. The system of claim 17 , wherein length l of the laser beam focal line is between 0.3 mm and 10 mm.
19. The system of claim 1 , wherein the laser is adapted to produce the laser beam that is a burst pulse laser beam, with each burst pulse comprising a plurality of pulses.
20. The system of claim 1 , wherein the optical arrangement is structured to aberrate the laser beam to form the laser beam focal line.
21. The system of claim 1 , wherein the laser beam focal line comprises a pattern of light rays having a linear shape, parallel to a beam axis of the laser beam.
22. The system of claim 1 , wherein the laser beam focal line comprises aberrated light rays that cross a beam axis of the pulsed laser beam at different positions along the beam axis.
23. The system of claim 1 , wherein the laser beam focal line comprises a length l that is greater than an average diameter δ of the laser beam focal line.
24. The system of claim 6 , wherein the diaphragm comprises a diameter that is 75% of a diameter of the second, focusing optical element.
25. The system of claim 1 , wherein an average diameter δ of the laser beam focal line is between 0.5 μm and 5 μm.
26. The system of claim 1 , wherein the first optical element and the second optical element are positioned and directed such that the laser beam strikes the second optical element in a collimated ring shape.
27. The system of claim 1 , wherein the laser comprises a non-ablative laser.
28. A system comprising:
a substrate; and
a device for laser-based machining, the device comprising:
a laser providing a laser beam of wavelength λ, such that a material of the substrate is transparent to the wavelength λ, a decrease in intensity of the laser beam taking place along the direction of the laser beam in the material of the substrate per millimeter of the depth of penetration is 10% or less,
an optical arrangement which is positioned in a path of rays of the laser beam, wherein:
the optical arrangement comprises a first optical element and a second, focusing optical element disposed on the beam output side of the first optical element at a distance z 1 from the first optical element; and
the first optical element and the second, focusing optical element are positioned and directed such that the laser beam strikes the second, focusing optical element is a ring shape, and a laser beam focal line extending along the direction of the laser beam is generated on the beam output side of the second, focusing optical element at a spacing z 2 from the second, focusing optical element; wherein:
the substrate comprises two opposite substrate surfaces and is positioned in relation to the laser beam focal line such that an extended segment of the induced absorption takes place in the material of the substrate along a single continuous cracking zone, such that induced crack formation is brought about in the material of the substrate along the extended segment of induced absorption;
the laser beam focal line extends up to at least one of the two opposite substrate surfaces,
the average diameter δ of the laser beam focal line is between 0.5 μm and 5 μm, and
the average laser power, measured directly on the output side of the laser beam is between 10 watts and 100 watts.
29. The system of claim 28 , wherein the first optical element comprises a non-spherical free surface.
30. The system of claim 29 , wherein the first optical element with a non-spherical free surface is a conical prism or axicon.
31. The system of claim 28 , wherein the device for laser based machining further comprises a third optical element, which is positioned between the first optical element and the second, focusing optical element in the path of rays of the laser beam, wherein the third optical element comprises a collimation lens.
32. The system of claim 28 , wherein the laser beam is a burst pulse laser beam, with each burst pulse comprising a plurality of pulses.
33. The system of claim 32 , wherein the burst pulse has a repetition frequency in a range of between 10 kHz and 1000 kHz.
34. The system of claim 28 , wherein the optical arrangement is structured to aberrate the laser beam to form the laser beam focal line.
35. The system of claim 28 , wherein the laser beam focal line comprises a pattern of light rays having a linear shape, parallel to a beam axis of the laser beam.
36. The system of claim 28 , wherein the laser beam focal line comprises aberrated light rays that cross a beam axis of the pulsed laser beam at different positions along the beam axis.
37. The system of claim 28 , wherein the laser beam focal line comprises a length l that is greater than the average diameter δ of the laser beam focal line.
38. The system of claim 28 , wherein the first optical element and the second, focusing optical element are positioned and directed such that the laser beam strikes the second, focusing optical element in a collimated ring shape.
39. The system of claim 28 , wherein the laser comprises a non-ablative laser.