Device and method for dividing materials

Abstract

The present invention relates to a method for dividing a workpiece (1) having a transparent material, wherein a material modification (5) is introduced into the transparent material of the workpiece (1) along a dividing line (4) by means of ultrashort laser pulses of an ultrashort pulse laser (2), and subsequently the material of the workpiece (1) is divided along the resulting material modification surface (50) by a dividing step, wherein the laser pulses are brought onto the workpiece (1) at an attack angle (α), and the material modification (5) is of type I and / or type II modification associated with a refractive index change of the material of the workpiece (1).

Description

Technical Field

[0001] This invention relates to an apparatus and method for dividing materials using ultrashort laser pulses. Background Technology

[0002] In recent years, the development of lasers with very short pulse lengths (especially those below one nanosecond) and high average power (especially in the kilowatt range) has led to a new type of materials processing. The short pulse length and high pulse peak power, or high pulse energy from a few microjoules to 100 μJ, can cause nonlinear absorption of the pulse energy within the material, resulting in the ability to process materials that are virtually transparent or essentially transparent to the laser wavelength used.

[0003] The specific application of this laser radiation lies in the cutting and processing of workpieces. In this process, the laser beam is preferably introduced into the material perpendicularly, as this minimizes reflection losses at the material surface. However, for processing materials at a certain angle of attack, such as chamfering material edges or creating chamfered and / or beveled structures with angles of attack greater than 30°, unresolved problems remain, especially because the large angle of attack at the material edges causes significant aberrations in the laser beam, making it impossible to achieve the target energy deposition within the material. Summary of the Invention

[0004] Based on known prior art, the objective of this invention is to provide an improved device for dividing workpieces and a corresponding method.

[0005] This task is accomplished by the method for dividing workpieces according to the present invention. Advantageous extensions of the method are derived from preferred embodiments, this specification, and the accompanying drawings.

[0006] Correspondingly, a method for segmenting workpieces with transparent materials is proposed, wherein material modification is introduced into the transparent material of the workpiece along a segmentation line by means of an ultrashort laser pulse from an ultrashort laser, and the workpiece is subsequently segmented along the resulting material-modified surface using a segmentation step. According to the invention, the laser pulse is introduced into the transparent material of the workpiece at an angle of attack, and the material modification is a type I and / or type II modification related to the refractive index change of the transparent material of the workpiece.

[0007] Ultrashort pulse lasers provide ultrashort laser pulses. Here, "ultrashort" can mean, for example, a pulse length between 500 picoseconds and 10 femtoseconds, and especially between 10 picoseconds and 100 femtoseconds. Here, the ultrashort laser pulses travel along the laser beam they form in the beam propagation direction.

[0008] When an ultrashort laser pulse is focused onto the material of a workpiece, the intensity in the focused volume can be nonlinearly absorbed, for example, through multiphoton absorption and / or electron avalanche ionization processes. This nonlinear absorption induces the generation of electron-ion plasma, which, upon cooling, can cause permanent structural changes within the workpiece material. Because energy can be transferred into the material volume through nonlinear absorption, these structural changes can be generated within the sample without affecting the workpiece surface.

[0009] Transparent material is understood herein as a material that is substantially transparent to the wavelength of the laser beam of an ultrashort pulse laser. The terms "material" and "transparent material" are used interchangeably here, meaning that the material referred to herein is always understood to be a material transparent to the laser beam of an ultrashort pulse laser.

[0010] Material modification introduced into transparent materials via ultrashort laser pulses is categorized into three distinct levels, as described by K. Itoh et al., "Ultrafast Processes for Bulk Modification of Transparent Materials," MRS Bulletin, vol. 31, p. 620 (2006): Type I is an isotropic refractive index change; Type II is a birefringent refractive index change; and Type III is the so-called void or cavity. The resulting material modification depends on laser parameters (such as pulse duration, wavelength, pulse energy, and repetition rate), material properties (especially electronic structure and coefficient of thermal expansion), and the focused numerical aperture (NA).

[0011] The isotropic refractive index variation of type I is attributed to the localized, confined melting by the laser pulse and the rapid resolidification of the transparent material. For example, in the case of quartz glass, the material has a higher density and refractive index when it is rapidly cooled from a higher temperature. Therefore, if the material in the focused volume melts and is subsequently rapidly cooled, the quartz glass has a higher refractive index in the modified region than in the unmodified region.

[0012] Type II birefringence refractive index changes can be generated, for example, through interference between an ultrashort laser pulse and the plasma electric field generated by the laser pulse. This interference causes periodic modulation of the electron plasma density, which induces birefringence in transparent materials during solidification, i.e., a direction-dependent refractive index. Type II modification is also related, for example, to the formation of so-called nanogratings.

[0013] For example, high laser pulse energy can be used to generate type III modified cavities. Here, the formation of cavities is attributed to the explosive expansion of highly excited, evaporated material from the focused volume to the surrounding material. This process is also known as micro-explosion. Because this expansion occurs within the mass of the material, micro-explosions leave behind a low-density or hollow core (void) surrounded by a dense material shell, or submicron or atomic-level defects. Stress is generated in transparent materials through the compressive effect at the impact leading edge of the micro-explosion; these stresses may lead to or promote crack formation.

[0014] The formation of voids is particularly relevant to Type I and Type II modifications. For example, Type I and Type II modifications can generate voids in regions of low stress around the introduced laser pulse. Therefore, if Type III modification is introduced, a low-density or hollow core or defect will inevitably appear. For example, in sapphire, in the case of Type III modification, cavities are not generated by micro-explosions, but rather regions of low density are created. Based on the material stress generated during Type III modification, such modification is usually accompanied by crack formation or at least promotes crack formation. With the introduction of Type III modification, it is impossible to completely prevent or avoid the formation of Type I and Type II modifications. Therefore, it is unlikely to find “pure” Type III modification.

[0015] With high laser repetition rates, materials cannot be completely cooled between pulses, thus the cumulative effect of heat introduced from pulse to pulse can influence material modification. For example, the laser repetition frequency can be higher than the reciprocal of the material's thermal diffusion time, allowing heat accumulation in the focused area through continuous absorption of laser energy until the material's melting temperature is reached. By transferring heat energy to the area surrounding the focused area, a region larger than the focused area can also be melted. Introducing ultrashort laser pulses causes rapid cooling of the heated material, thereby freezing, to some extent, the density and other structural properties at the high temperature within the material.

[0016] Material modification is introduced into the material along the dividing line. The dividing line describes the incident line of the laser beam on the workpiece surface. For example, by feed, the laser beam and the workpiece move relative to each other with the feed rate, thus resulting in different incident positions of the laser pulses on the workpiece surface over time. Here, the laser feed rate and / or repetition rate are selected such that the material modification in the workpiece material does not overlap, but exists separately from each other in the material. Relative to each other's movement here means that the laser beam can be translated relative to the fixed workpiece, and the workpiece can also move relative to the laser beam. Movement of both the workpiece and the laser beam is also possible. During the movement of the workpiece and the laser beam relative to each other, the ultrashort pulse laser emits laser pulses into the workpiece material at its repetition frequency.

[0017] By modifying the material along the direction of beam propagation, a plane is created in the workpiece material, in which all material modifications exist and which intersect the workpiece surface along a dividing line. The plane containing the material modifications is called the material modification surface. The material modification surface can also be curved; therefore, for example, material modifications forming the outer surface of a cylinder or cone also exist in the material modification surface.

[0018] The laser pulse is introduced into the workpiece material at a so-called angle of attack. Here, the angle of attack is given as the angular difference between the laser beam and the surface normal of the workpiece to be divided. When the angle of attack is not zero, the material modification surface is also inclined relative to the surface normal of the workpiece. It should be noted that when the angle of attack is non-zero, the laser beam is refracted according to Snell's law of refraction, depending on the refractive index of the surrounding medium (preferably air) and the workpiece material. Thus, the beam propagation direction in the workpiece material can be different from the beam propagation direction before it is incident on the workpiece material. Consequently, the material modification surface can also be inclined relative to the surface normal at an angle different from the angle of attack.

[0019] Type I and Type II modifications are used here to create predetermined fracture points in the material or to weaken the material along the modification surface. The material weakening introduced by Type I and Type II can be achieved by segmenting the material along the modification surface.

[0020] Here, the workpiece is divided into large parts and so-called segments by segmentation along the material modification surface through a segmentation step.

[0021] Here, the partitioning step may include mechanical partitioning and / or chemical partitioning steps, preferably an etching process and / or thermal application and / or self-partitioning steps.

[0022] Heat application can be achieved, for example, by heating the material or the dividing lines or surfaces. The dividing lines or surfaces can be locally heated, for example, by means of a continuous-wave CO2 laser, causing the material in the modified region to expand to different degrees compared to the untreated or unmodified material. However, it is also possible to apply heat via a hot gas flow, by baking on a hot plate, or by heating the material in a furnace. In particular, a temperature gradient can be introduced during the dividing step to induce different degrees of thermal expansion in the material. Finally, the material modification and the resulting weakening can promote crack formation in the modified surfaces, thus creating continuous and seamless dividing surfaces that separate parts of the workpiece from each other.

[0023] Mechanical segmentation can be achieved by applying tensile or bending stresses, for example, by applying a mechanical load to the portion of the workpiece separated by a dividing line or plane. For example, tensile stress can be applied when opposing forces in the material plane act at the points of force engagement on the portion of the workpiece separated by a dividing line or plane (these forces are directed away from the dividing line or plane). Bending stress can be generated if these forces are not parallel or are antiparallel to each other. Once the tensile or bending stress exceeds the binding force of the material along the dividing line or plane, the workpiece is segmented along the dividing plane. Mechanical changes can also be achieved, in particular, by pulsed action on the portion to be segmented. For example, lattice vibrations can be generated in the material by impact. Due to the deflection of lattice atoms, tensile and compressive stresses can also be generated, which can trigger crack formation in the modified material plane. However, material segmentation is preferably achieved by etching using a wet chemical solution, where the etching process preferably acts on the material at the modified area, i.e., targeted material weakening. In other words, selective etching capability is increased by introducing material modification. This achieves workpiece segmentation along the segmentation plane by preferably etching the portion of the workpiece that has been weakened through material modification.

[0024] The advantage of this is that an ideal segmentation method can be selected for the corresponding material of the workpiece, so that the segmentation of the workpiece is accompanied by high-quality segmentation edges.

[0025] Material modification can also be introduced through heat accumulation in the workpiece material.

[0026] If the pulse rate of the laser beam is greater than the rate of heat transfer through the material-specific heat transfer mechanism, heat accumulation can be achieved through continuous absorption of ultrashort laser pulses. As the temperature in the workpiece material rises, it eventually reaches the melting temperature of the weldment material, causing localized melting. This can result in type I and / or type II modifications, as described above, particularly in the workpiece material.

[0027] To melt the material of a workpiece, a large number of laser pulses can be emitted at locations within the material, where these locations must be sufficiently overlapping spatially to allow heat accumulation even with a feed. The pulse overlap can be greater than 1, thus allowing more than one pulse to be emitted at each incident location.

[0028] Here, the spatial overlap must be greater than 1, given by df*R / V, where df is the beam diameter or the diameter of the transverse intensity distribution (see below), R is the laser repetition frequency, and V is the feed rate. Furthermore, the time pulse interval must be less than the diffusion time tD in the material, given by tD = (df / 2)^2 / 2D, where D = kappa / (rho*cp) is the diffusivity, kappa is the thermal conductivity, cp is the specific heat capacity, and rho is the density of the material. For example, the diffusion time of fused silica is 1 μs.

[0029] By continuously heating and melting the material, a segmentation process can produce a segmented surface of exceptionally high quality.

[0030] In particular, it can be proposed that the material modification penetrates the two sides of the workpiece located at the intersecting plane, and produces bevels and / or shaped edges, preferably chamfers and / or bevels, through a segmentation step.

[0031] When the surface normals of a plane are not oriented parallel to each other, the two side faces lie in intersecting planes. For example, in the case of a cuboid, when the two side faces can be connected by the edges of the cuboid, these two side faces lie in intersecting planes. In the case of a disc-shaped material, the circumference of the disc lies to some extent in planes intersecting with the upper and lower sides of the disc. At least locally, in the case of a disc, a rectangular cross-section is produced in the incident plane of the laser beam.

[0032] Material modification penetrates two adjacent sides. Penetration here means that the material modification begins on one side and ends on the other side along the beam propagation direction. However, it can also mean that the material modification extends only within the workpiece material to avoid cracks on the material surface. In this case, however, most of the laser path between the two sides must be altered by the material modification. For example, by strategically positioning the material modification within the material, introducing it only in one-third of the path may be sufficient. However, it is also feasible for the material modification to be continuous throughout the entire path between the two sides.

[0033] Thus, a segment of the workpiece is created in the incident plane of the laser beam, in which both the incident and refracted beams lie. For example, in the case of a cuboid, this segment can be triangular. The triangular segment of the workpiece has a so-called hypotenuse opposite the edge to be divided. Here, the length of the hypotenuse is given by the length of the material modification in the workpiece. Furthermore, the spacing between the sides connected to the hypotenuse of the segment is given by the distance between the dividing line and the edge of the workpiece.

[0034] Because the material modification penetrates both sides of the material, a predetermined fracture point is introduced along the entire length of the hypotenuse. Therefore, in the subsequent segmentation step, the workpiece is segmented along the material-modified surface.

[0035] The modified surfaces of the material, after segmentation, become what are called shaped edges of the material. The shaped edges of the workpiece are further subdivided into what are called chamfers and bevels. A chamfer is understood here as a beveling, where the original edge of the cuboid is replaced by two edges. This softens the original edge or provides a transition area from the first cuboid side to the second cuboid side. A bevel is created when the bevel of a segment coincides with an edge of the workpiece, or typically when one side of a triangular segment matches the length of at least one of the workpiece's parallel-extending sides.

[0036] For example, the bevel of the chamfer and / or bevel is between 50 μm and 500 μm, preferably between 100 μm and 200 μm.

[0037] The advantages of this are that the workpiece can be beveled in a visually appealing and high-quality manner. Furthermore, it allows for beveling of thicker workpieces. By providing shaped edges, chamfers, or bevels, more stable edges can be achieved, which are less prone to breakage during further processing, installation, or use by the end customer compared to edges at a 90° angle.

[0038] A laser beam can be a non-diffractive laser beam.

[0039] Non-diffractive beams and / or Bessel beams are particularly understood as beams in which there is no propagation difference in the transverse intensity distribution. In the case of non-diffractive beams and / or Bessel beams, the transverse intensity distribution is generally constant, especially along the longitudinal direction and / or propagation direction of the beam.

[0040] The transverse intensity distribution is understood as the intensity distribution located in a plane oriented perpendicular to the longitudinal direction and / or propagation direction of the beam. Furthermore, the intensity distribution is always understood as the portion of the laser beam's intensity distribution that exceeds the material modification threshold. This can, for example, mean that only a few or even a small number of maximum intensities from a non-diffractive beam can introduce material modification into the workpiece material. Correspondingly, the term "focused region" can also be used for intensity distribution to indicate that this portion of the intensity distribution is provided in a targeted manner and that an increase in intensity in the form of an intensity distribution is achieved through focusing.

[0041] For the definition and properties of non-diffractive beams, please refer to the book, "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M. Springer Science & Business Media (2012), ISBN 978-3-642-29322-1 [Structured light fields: applications in optical capture, manipulation and organization, author M.] Springer Science & Business Media (2012), ISBN 978-3-642-29322-1. This article is explicitly and fully cited herein.

[0042] Accordingly, non-diffractive laser beams have the advantage that they can have an elongated intensity distribution along the beam propagation direction, which is significantly larger than the transverse dimension of the intensity distribution. This can, in particular, produce material modification that elongates along the beam propagation direction, allowing the material modification to penetrate both sides of the workpiece particularly easily.

[0043] The laser beam can have a non-radial symmetrical transverse intensity distribution, wherein the transverse intensity distribution is elongated on the first axis compared to the second axis, and the second axis is perpendicular to the first axis.

[0044] Non-radial symmetry here means that the transverse intensity distribution depends not only on the distance from the optical axis, but also at least on the polar angle around the beam propagation direction. A non-radial symmetric transverse intensity distribution can, for example, be cross-shaped, triangular, or N-shaped, such as pentagonal. A non-radial symmetric transverse intensity distribution can also include further rotationally symmetric and mirror-symmetric beam cross sections. A non-radial symmetric transverse intensity distribution can also, in particular, have an elliptical shape, where the ellipse has a major axis A and a minor axis B perpendicular to it. An elliptical transverse intensity distribution exists correspondingly when the ratio A / B is greater than 1, especially A / B = 1.5. An elliptical transverse intensity distribution of a laser beam can correspond to an ideal mathematical ellipse. However, a non-radial symmetric transverse intensity distribution of a non-diffractive laser beam can also have only the ratio derived from the aforementioned major and minor axes, but with other contours, such as an approximate mathematical ellipse, a dumbbell shape, or other symmetric or asymmetric contours contained within a mathematically ideal ellipse.

[0045] In particular, elliptical non-diffractive beams can be generated from non-diffractive beams. Here, the elliptical non-diffractive beam possesses special characteristics derived from the analysis of beam intensity. An elliptical quasi-non-diffractive beam, for example, has a principal maximum value coinciding with the center of the beam. The center of the beam is given here by its position intersecting the principal axis. An elliptical quasi-non-diffractive beam can also be generated, in particular, by the superposition of multiple maximum intensities, where in this case only the envelope of the maximum intensities involved is elliptical. Each maximum intensity need not necessarily have an elliptical intensity profile.

[0046] Due to the non-radial symmetric transverse intensity distribution, the material modification is also non-radial symmetric in the cross-section perpendicular to the beam propagation direction in the material. Furthermore, the shape of the modified material corresponds to the intensity distribution of the non-diffractive beam within the workpiece material.

[0047] In non-diffractive beams, there are particularly high-intensity regions that interact with the material and introduce material modification, as well as regions below the modification threshold. The non-radially symmetric transverse intensity distribution here is related to the maximum intensity above the modification threshold.

[0048] If the feed direction is, for example, parallel to the long axis of the transverse intensity distribution, large pulse overlap can be generated particularly easily, thereby increasing the feed rate. This makes the segmentation process faster and more cost-effective.

[0049] In the projection of the non-radially symmetric transverse intensity distribution onto the surface of the workpiece, the first axis and the second axis appear to be of equal size due to the angle of attack.

[0050] A non-radially symmetric transverse intensity distribution, when mathematically projected onto the workpiece surface at an angle of attack, can lead to distortion of the intensity distribution. Therefore, for example, a circular intensity distribution can be generated on the workpiece from an initially elliptical intensity distribution. However, it can also be achieved, in particular, by realizing an elliptical projection onto the workpiece surface using an initially circular intensity distribution. This introduces material modifications into the material, resulting in an intensity distribution obtained by projecting it onto the workpiece surface at an angle of attack.

[0051] Thus, it is also possible to project the previously selected preferred direction to distort the non-radially symmetric transverse intensity distribution and thus deviate the preferred direction from the actual effective intensity distribution.

[0052] Therefore, in the preferred embodiment, the non-radially symmetrical lateral strength distribution is circular due to the angle of attack. This specifically means that, in the case of an initially elliptical lateral strength distribution, the major axis A and minor axis B of the ellipse appear to be of equal size due to projection. Thus, the circular strength distribution effectively produces material modification.

[0053] The projection of a non-radial symmetric intensity distribution onto the workpiece surface can be elongated in the feed direction.

[0054] This allows for the control of distortion by projecting the intensity distribution onto the workpiece surface, ensuring that the long axis of the transverse intensity distribution points towards the feed direction. Since the preferred direction points towards the feed direction and thus extends parallel to the dividing line, the workpiece can be divided along the resulting material-modified surface with particularly easy and high-quality cutting.

[0055] The material modification surface can be tilted relative to the surface of the workpiece at an angle of up to 35°.

[0056] According to Snell's law of refraction, the product of the refractive index of the surrounding medium and the sine of the angle of attack corresponds to the product of the refractive index of the material and the sine of the angle of refraction. Correspondingly, the angle of attack can be selected based on the refractive index, such that the material-modified surface is tilted at a maximum of 35° relative to the workpiece surface. In particular, the angle description relates to the material-modified surface, in which material modification exists, thus making this angle directly correspond to the angle of refraction.

[0057] The pulse energy of the laser pulse can be between 10 μJ and 50 mJ, and / or the average laser power can be between 1 W and 1 kW, and / or the laser pulse can be a single laser pulse or part of a laser burst, and / or the wavelength of the laser can be between 300 nm and 1500 nm, especially 1030 nm.

[0058] The advantage of this is that it can provide optimal laser parameters for different materials.

[0059] For example, an ultrashort pulse laser can provide a single laser pulse with a pulse energy of 100 μJ, an average laser power of 5 W, and a laser wavelength of 1030 nm.

[0060] A laser burst can include 2 to 20 laser pulses, wherein the laser pulses of the laser burst have a time interval of 10 ns to 40 ns, preferably 20 ns.

[0061] A laser burst can, for example, consist of 10 laser pulses with a time interval of 20 ns. In this case, the repetition frequency of the laser pulses is 50 MHz. Alternatively, the laser burst can be emitted with a repetition frequency of a single laser pulse on the order of 100 kHz.

[0062] By using laser bursts, the specific thermal properties of the material can be taken into account, thus producing shaped edges with exceptionally high surface quality.

[0063] In the first method step, a material modification extending parallel to the surface normal of the workpiece can be introduced into the workpiece material; in the second method step, a material modification extending at an angle relative to the surface normal of the workpiece can be introduced into the workpiece material, wherein the material modification surface of the second method step intersects with the material modification surface of the first method step, wherein a segmentation step is performed after the second method step.

[0064] Here, a first method step introduces material modification into the workpiece material, which determines the workpiece's external dimensions after the slitting step. A second method step introduces material modification into the workpiece material, which is then used to create chamfers or bevels through the slitting step.

[0065] Here, the segmentation step can be performed after the first and second method steps, thus requiring two modification steps and two segmentation steps each. However, the material modification for fixed-length cutting and beveling can also be introduced into the workpiece material in the first step and the segmentation can be performed in a common segmentation step. This can save at least one segmentation step, thereby allowing the method to be performed in a particularly time-efficient manner.

[0066] An incident laser beam can be polarized parallel to the incident plane.

[0067] The refraction of a laser beam during its transition from the surrounding medium to the workpiece material depends not only on the angle of attack and the refractive index. In this case, the polarization of the laser beam also plays a crucial role. The so-called Fresnel equations state that when the angle of incidence is greater than 10°, the transmittance of a laser beam polarized parallel to the plane of incidence is always greater than that of a laser beam polarized perpendicular to the plane of incidence.

[0068] In particular, P-polarization can minimize the reflection loss of the laser beam, thereby achieving optimal energy output in the material segmentation process. Furthermore, when the laser beam is incident at a Brewster-Winkel angle, energy coupling that is particularly advantageous to the material can be achieved.

[0069] The objectives stated above are also achieved by the apparatus for dividing workpieces according to the present invention. Preferred embodiments, the description, and the accompanying drawings reveal advantageous extensions.

[0070] Correspondingly, an apparatus for segmenting a workpiece comprising a transparent material is proposed, the apparatus comprising: an ultrashort pulse laser configured to provide an ultrashort laser pulse; a processing optical tool configured to introduce the laser pulse into the transparent material of the workpiece; and a feeding device configured to move the laser beam of the laser pulse and the workpiece relative to each other along a segmentation line and to orient the optical axis of the processing optical tool relative to the surface of the workpiece at an angle of attack. According to the invention, the laser pulse is introduced into the transparent material of the workpiece at an angle of attack, wherein the material modification is a type I and / or type II modification related to a change in the refractive index of the workpiece material.

[0071] The processing fixture can be, for example, an optical imaging system. It can consist of one or more components. These components can be, for example, lenses, freeform optical imaging surfaces, or Fresnel zone plates. The processing fixture allows for the determination of the depth to which the intensity distribution is introduced into the workpiece material. To a certain extent, the positioning of the focal zone can be adapted in the beam propagation direction. Therefore, the focal zone can be positioned on the surface of the workpiece, or preferably within the workpiece material, for example, by adjusting the processing fixture. The focal zone can be adapted, for example, such that the laser beam penetrates adjacent side surfaces and thus produces material modification, which allows for the complete segmentation of the workpiece by means of a segmentation step.

[0072] Here, the feed device can be, for example, an XY or XYZ stage to change the incident point of the laser pulse on the workpiece. The feed device can move the workpiece and / or the laser beam so that material modification can be introduced into the workpiece material side-by-side along the dividing line.

[0073] The feed device can also be angle-adjustable, allowing the workpiece and laser beam to rotate relative to each other by all Euler-Winkel angles. This, in particular, ensures that the angle of attack is maintained along the entire dividing line.

[0074] Here, the angle of attack is also understood as the angle between the optical axis of the machining tool and the surface normal of the workpiece material. The angle of attack between the optical axis of the machining tool and the surface normal can, for example, be between 0 and 60°.

[0075] A beamforming optical tool can form a non-diffractive laser beam from a laser beam, wherein the transverse intensity distribution of the non-diffractive laser beam can be non-radially symmetrical, wherein the non-radially symmetrical transverse intensity distribution can be elongated along the first axis compared with the second axis, and wherein the second axis is perpendicular to the first axis.

[0076] Beamforming optical systems can be designed as diffractive optical systems (DOEs), freeform surfaces implemented by reflection or refraction, or axial or microaxial conicals, or combinations of multiple such components or functions. When a beamforming optical system forms a non-diffractive laser beam in front of a processing optical system using a laser beam, the depth of introduction of the intensity distribution in the material can be determined by focusing the processing optical system. However, beamforming optical systems can also be designed such that a non-diffractive laser beam is generated solely by imaging using the processing optical system.

[0077] A diffractive optical element is configured to influence one or more properties of an incident laser beam in two spatial dimensions. A diffractive optical element is a fixed component that can be used to precisely generate the intensity distribution of a non-diffractive laser beam from an incident laser beam. Typically, a diffractive optical element is a specially shaped diffraction grating, where diffraction causes the incident laser beam to form a desired beam shape.

[0078] An axial cone is a conically ground optical element that forms a non-diffractive laser beam by passing an incident Gaussian laser beam through it. The axial cone has a cone angle α, calculated from the beam incident surface and the outer surface of the cone. As a result, the edge of the Gaussian laser beam is refracted to a focal point different from the beam closer to the axis. This results in an elongated intensity distribution along the beam propagation direction.

[0079] The machining optical tool includes a telescope system configured to introduce a reduced and / or magnified laser beam into the material of the workpiece.

[0080] Enlarging and / or reducing the intensity distribution of a laser beam or its transverse intensity allows the laser beam intensity to be distributed over a large or small focal area. By adapting the intensity to a large or small area, it is possible to select between type I, type II, and type III modifications, especially through enlargement and / or reduction.

[0081] In particular, amplified or reduced material modification can be introduced into the workpiece material by amplifying or reducing the non-radially symmetric transverse intensity distribution. For example, since the elliptical transverse intensity distribution is introduced into the material in a reduced manner, the radius of curvature of the introduced material modification is also reduced. In other words, a given curvature becomes sharper by reduction. This can be beneficial for crack formation in the workpiece material. Furthermore, the optical system can be adapted to given processing conditions by amplifying or reducing it, allowing for more flexible use of the device.

[0082] The feeding device may include a shaft device and a workpiece holder, which are configured to move the machining optical element and the workpiece relative to each other in a manner that translates along three spatial axes and rotates about at least two spatial axes.

[0083] Axis devices can be, for example, 5-axis devices. Axis devices can also be, for example, robotic arms that guide a laser beam on a workpiece or move a workpiece relative to a laser beam.

[0084] Because the laser beam and the workpiece move relative to each other to introduce material modification along the dividing line, either the laser beam or the workpiece needs to be locally rotated to maintain the angle of attack relative to the dividing line. Therefore, even when the dividing line is curved, the material modification surface always maintains the same angle relative to the workpiece surface.

[0085] In particular, such a shaft device can simultaneously achieve: a non-radial symmetric transverse strength distribution oriented relative to the dividing line, such that the material modification that produces its preferred direction extends parallel to the dividing line and promotes crack formation along it.

[0086] Furthermore, the axis device may also include fewer than five movable axes, as long as the workpiece holder can move about the corresponding number of axes. For example, if the axis device is movable only in the XYZ directions, the workpiece holder may have, for example, two rotational axes to rotate the workpiece relative to the laser beam.

[0087] The laser beam is directed at the workpiece at an incident angle of up to 80° relative to the surface normal of the workpiece.

[0088] A laser pulse is focused onto an optical axis by machining an optical tool, which is oriented at an angle of attack relative to the surface normal of the workpiece. Here, the sub-laser beams of the laser beam have angles relative to the optical axis of the machining tool. In particular, these angles can be very large or very small due to numerical aperture.

[0089] Because these sub-laser beams within the envelope of the laser beam fall onto the workpiece surface at angles greater than 80°, significant reflection losses can be avoided. According to Fresnel's formula, the reflection and transmittance of the laser beam on the workpiece surface depend on the angle of attack and the refractive index. In the case of grazing incidence, only a small fraction of the laser beam can couple into the material, thus hindering effective material processing. Furthermore, this may negatively impact non-diffractive beams.

[0090] The polarizing optical apparatus, preferably including a polarizer and a waveplate, can be configured to adapt the polarization of the laser beam relative to the incident plane of the laser beam, preferably in a manner parallel to the incident plane.

[0091] Waveplates, especially so-called λ / 2 waveplates, can rotate the polarization direction of linearly polarized light by a selectable angle. This allows the laser beam to achieve the desired polarization.

[0092] Polarizers can be, for example, thin-film polarizers. Thin-film polarizers transmit laser radiation with only a specific polarization.

[0093] Therefore, by combining waveplates and polarizers, the polarization state of laser radiation can be controlled at all times.

[0094] According to Fresnel's formula, the transmittance of a laser beam polarized parallel to the incident plane has the following advantages: the transmittance is consistently higher when the laser beam is polarized perpendicular to the incident plane than when the laser beam is polarized perpendicular to the incident plane. In particular, compared to the case of perpendicularly polarized light, the transmittance of a parallel-polarized laser beam is more constant and uniform over a large angle-of-attack range. This allows for the use of machining tools with large numerical apertures. In the case of perpendicularly polarized laser beams, this results in asymmetric reflection of the beam on the workpiece surface, thus reducing optical aberrations and consequently degrading material modification and the quality of the cleaved surface.

[0095] The beam guiding device can be configured to guide a laser beam to a workpiece, wherein the beam guiding is performed by means of a mirror system and / or optical fiber, preferably hollow optical fiber.

[0096] So-called free-beam guiding uses a mirror system to guide the laser beam of a fixed ultrashort pulse laser along different spatial dimensions to a beamforming optical tool. The advantage of free-beam guiding is that the entire optical path is accessible, so other components, such as polarizers and waveplates, can be easily mounted.

[0097] Hollow-core fiber is a photonic fiber that can flexibly transmit the laser beam from an ultrashort pulse laser to a beamforming optical fixture. Using hollow-core fiber eliminates the need for adaptation of reflector optical fixtures.

[0098] The adjustment electronics can be configured to trigger the emission of laser pulses from the ultrashort pulse laser based on the relative position of the laser beam and the workpiece.

[0099] In cases of curved or angular feed trajectories, locally reducing the feed rate can be beneficial. However, with a constant laser repetition frequency, this can lead to uneven formation of the material modification surface, and thus prevent the achievement of uniform surface quality during the dicing step. For this reason, the control electronics can adjust the pulse emission based on the relative position of the laser beam and the workpiece.

[0100] For example, the feeding device can have a position-resolved encoder that measures the position of the feeding device and the laser beam. Based on the position information, the pulse emission of the laser pulse can be triggered in the case of an ultrashort pulse laser by adjusting the corresponding triggering system of the electronic device.

[0101] In particular, computer systems can be used to implement pulse triggering. For example, the position of the laser pulse emission can be determined before processing the material for the corresponding dividing line, thereby ensuring the optimal distribution of material modification along the dividing line.

[0102] This ensures that the spacing between material modifications remains constant even when the feed rate changes. Furthermore, it allows for the production of uniformly sized surfaces and high-quality chamfers or bevels.

[0103] The workpiece holder may have a surface that does not reflect and / or scatter laser beams.

[0104] This, in particular, prevents the laser beam from being redirected back into the material after it has penetrated it, thus preventing further material modification at that point. Non-reflective and / or non-scattering surfaces also significantly improve operational safety. Attached Figure Description

[0105] Other preferred embodiments of the invention will be described in detail below with reference to the accompanying drawings. In the drawings:

[0106] Figure 1A , Figure 1B , Figure 1C , Figure 1D A schematic diagram of the method is shown;

[0107] Figure 2A , Figure 2B , Figure 2C A schematic diagram showing the chamfered and beveled structure is shown;

[0108] Figure 3A , Figure 3B , Figure 3C , Figure 3D , Figure 3E , Figure 3F Another schematic diagram showing the chamfered and beveled structure is shown;

[0109] Figure 4A , Figure 4B A schematic diagram of a non-diffractive laser beam is shown.

[0110] Figure 5A , Figure 5B , Figure 5C , Figure 5D , Figure 5E Another schematic diagram of a non-diffractive laser beam is shown;

[0111] Figure 6 A schematic diagram showing material modification is shown;

[0112] Figure 7A , Figure 7B A schematic diagram showing the projection of the beam onto the material surface;

[0113] Figure 8A , Figure 8B , Figure 8C , Figure 8D Another schematic diagram showing the projection of the beam onto the material surface;

[0114] Figure 9 A graph is shown to illustrate transmittance based on polarization and angle of attack;

[0115] Figure 10 A schematic diagram showing an apparatus for performing the method; and

[0116] Figure 11A , Figure 11B , Figure 11C Another schematic diagram of the apparatus for performing the method is shown. Detailed Implementation

[0117] Preferred exemplary embodiments are described below with reference to the accompanying drawings. Here, in different drawings, the same reference numerals are used for the same, similar, or identical elements, and repeated descriptions of these elements are partially omitted to avoid redundancy.

[0118] Figure 1 schematically illustrates a method for dividing a workpiece 1, which includes transparent material. Figure 1A The image shows a cross-section of workpiece 1, onto which the laser beam 20 of an ultrashort pulse laser 2 is incident. Here, the laser beam 20 is introduced onto workpiece 1 at an angle of attack α, which corresponds to the optical axis of the machining fixture 3 shown below.

[0119] Upon transition to workpiece 1, the laser beam 20 is refracted at surface 10 of workpiece 1 according to Snell's law of refraction, causing the laser beam 20 to continue propagating in the material of workpiece 1 at an angle β relative to the surface normal N. Since the laser pulse is introduced into workpiece 1 through the laser beam 20, the material of workpiece 1 in the focusing region 220 of the laser beam 20 is heated, preferably by heat accumulation. Here, the material of workpiece 1 melts in the focusing region of the laser beam, wherein the material of workpiece 1 has a different refractive index compared to its initial state upon recooling. The modification of the material of workpiece 1 in the focusing region 220 is referred to as material modification 5, wherein material modification 5 is particularly type I or type II material modification. Due to the material modification 5, the material of workpiece 1 is selectively weakened, thereby allowing for targeted segmentation of material 1 through a segmentation step.

[0120] Here, the pulse energy of the laser pulse can be between 10 μJ and 50 mJ, and / or the average laser power can be between 1 W and 1 kW, and / or the laser pulse can be a single laser pulse or part of a laser burst, and / or the wavelength of the laser can be between 300 nm and 1500 nm. Furthermore, it is possible that the laser burst comprises 2 to 20 laser pulses, wherein the laser pulses of the laser burst have a time interval of 10 ns to 40 ns, preferably 20 ns.

[0121] During the emission of laser pulses by the ultrashort pulse laser 2, the laser beam 20 and the workpiece 1 move relative to each other with a feed V, such as Figure 1B As shown in the diagram, the feed V is guided along the dividing line 4, which determines where the workpiece 1 should be divided on the upper side 10. Since the laser beam 20 propagates within the material of the workpiece 1 at an angle β, the material modification 5 is also introduced into the material of the workpiece 1 at an angle β. In particular, the material modification 5 can be shaped differently depending on the extension scale and configuration or intensity distribution of the focusing region 220, especially being elongated in the beam propagation direction.

[0122] When the material modification 5 is elongated in the beam propagation direction, the laser beam 20 simultaneously feeds V, creating a so-called material modification surface 50 in the material of the workpiece 1 where the material modification 5 is located. The material modification surface 50 is preferably uniformly introduced into the material of the workpiece 1, which can be achieved through sufficient pulse overlap of the laser pulses in the material 1. The workpiece 1 is divided into a so-called main body workpiece 1' and a so-called segment 12 by the material modification surface 50. For example, the material modification surface 50 is inclined at an angle β with a maximum magnitude of 35° relative to the surface 10 of the workpiece 1.

[0123] Through material modification 5 in the material modification surface 50, the material of workpiece 1 can be specifically weakened, so that workpiece 1 and segment 12 can be separated from each other particularly easily along the material modification surface 50.

[0124] True segmentation can be achieved through specific segmentation steps. For example, segment 12 can be separated from the block workpiece 1' by chemical treatment. Segment 12 and the block workpiece 1' can be separated, for example, in a chemical bath, such as... Figure 1C As shown. For example, the introduced material modification 5 may be particularly susceptible to the effects of the etching solution, causing the etching process in the material-modified surface 50 to separate segment 12 from the block workpiece 1'. Correspondingly, the material modification 5 can also be selectively etched.

[0125] Through the above-described segmentation steps, so-called chamfers and / or bevels are created on the block-shaped workpiece 1', such as Figure 1D As shown. Similarly, the chamfer of workpiece 1 is known as the shaped edge of workpiece 1. The chamfer or bevel is formed by the material modification surface 50, such that the angle of attack α of the laser beam 20, the surrounding medium and the refractive index of workpiece 1 result in the angle of refraction β, and thus the orientation of the material modification 5 and the final chamfer or bevel is obtained.

[0126] To produce the shaped edge 14, it is advantageous that the material modification 5 passes through those sides of the edge of the workpiece 1 that should be beveled. For example, in Figure 1A In the middle, the sides 10 and 11 form an edge 110 that should be beveled. The sides 10 and 11 of the workpiece 1 are located in intersecting spatial planes, wherein the line of intersection of the planes is exactly the edge 110 of the workpiece 1.

[0127] exist Figures 2A to 2C The diagram illustrates various possible shaped edges of the material. Figure 2A In this process, the material-modified surface 50 intersects with the workpiece 1, wherein the height of the chamfer is less than the height of the side surface 11 and the width of the chamfer is less than that of the side surface 10. Correspondingly, the edge 110 is replaced by two edges 110' and 110" by beveling. As a result, the original edge 110 becomes particularly blunt or flat.

[0128] exist Figure 2B In this example, the material-modified surface 50 intersects with the workpiece 1, wherein the height of the segment 12 corresponds to the height of the side surface 11, and the material-modified surface 50 coincides with the edge 130 formed by the lower side 13 and the side surface 11 of the workpiece 1. In this example, the number of edges remains unchanged; however, the angle at which the sides 13 and 11 intersect becomes sharper. Correspondingly, the workpiece 1 can be sharpened and / or honed by forming the bevel 12.

[0129] exist Figure 2C In this process, the material modification surface 50 intersects with the workpiece 1, specifically intersecting not only the upper side 10 but also the lower side 13 of the workpiece 1. This reduces the overall longitudinal extension dimension of the workpiece 1 and, as in... Figure 2B The same process also makes workpiece 1 sharper.

[0130] In each of the cases shown, the length of the material modification in the material gives the so-called hypotenuse H of segment 12.

[0131] Even though the preceding description simplifies to dividing a cuboid, this method can also be used to divide circular material 1 or rounded material. For example, in Figure 3A , Figure 3B The image shows a workpiece 1 in the form of a disk. The so-called incident plane is defined by a laser beam 20 incident at an angle of attack α and a laser beam 20 refracted at an angle β. Within this incident plane, the previous description can be used verbatim.

[0132] exist Figure 3C The document also shows that... Figure 3A , Figure 3B The oblique cutting of the disc achieves a tapered component, which allows for the creation of different shapes on the forming edge through the introduction of material modification 5.

[0133] exist Figure 3D Another example is shown. Material modification 5 is introduced into workpiece 1 in a circumferential manner, wherein the dividing line 4 is curved and the angle of attack α remains constant in the incident plane. Thus, a rounded chamfer or bevel with high optical quality is produced after the dividing step.

[0134] exist Figure 3E Another example is shown here. Here, with... Figure 3D The difference lies in the absence of rounded dividing lines 4. The workpiece 1 is successively beveled on all four sides, resulting in crystalline chamfers at the corners of the workpiece 1 after the dividing step. This method is therefore also suitable for achieving a particularly high-quality appearance for the workpiece 1.

[0135] exist Figure 3F It shows Figure 3D and Figure 3FThe cross-section of material 1 is shown. The cross-section clearly shows the formation of chamfer 14.

[0136] To readily produce material modification 5 that penetrates at least a section of the workpiece 1, a so-called non-diffractive laser beam 20 is used. The non-diffractive beam 20 preferably has a focusing region 220 elongated along the beam propagation direction with a length of L. Since the length L of the focusing region 220 is greater than the desired length H of the bevel of the section 12, the workpiece 1 can be beveled particularly easily and efficiently.

[0137] exist Figure 4A The diagram schematically illustrates a laser beam 20 processed by a beamforming optical tool. Sub-laser beams 200 of the laser beam 20 are incident on the workpiece 1 at an angle α' relative to the optical axis 30, wherein each sub-laser beam 200 is refracted according to its angle α' relative to the optical axis 30. However, in this example of the laser beam 20, the optical axis 30 is generally perpendicular to the surface 10 of the workpiece 1, thus the angle of attack is 0°. In the workpiece 1, the sub-laser beams 200 are superimposed to form a non-diffractive beam having an elongated focusing region 220 of length L.

[0138] When the laser beam 20 is tilted, i.e., incident at a non-zero angle of attack α, aberrations will occur in the material because the upper half of the beam is incident on the workpiece at an angle α+α', while the lower half of the beam is incident on the workpiece 1 at an angle α-α'. This can cause the focusing area 220 to shorten or deform, such as... Figure 4B The figure shows an angle of attack of α = 15°. However, even using a laser beam without aberration correction, this method can produce material modification 5, wherein the hypotenuse H of the chamfer and / or bevel is between 50 μm and 500 μm, preferably between 100 μm and 200 μm.

[0139] exist Figure 5A The image shows the transverse intensity distribution or focusing region 220 of the non-diffractive laser beam 20. The non-diffractive laser beam 20 is a so-called Bessel-Gaussian beam, wherein the transverse intensity distribution is radially symmetrical in the xy-plane, such that the intensity of the non-diffractive laser beam 20 depends only on its radial distance from the optical axis 30. Specifically, the diameter of the transverse intensity distribution is between 0.25 μm and 10 μm. Figure 5B The image shows the longitudinal beam cross-section, i.e., the longitudinal intensity distribution. The longitudinal intensity distribution has a high-intensity elongated region, which is approximately 3 mm long. Therefore, the longitudinal extension scale of the focusing region 220 is significantly larger than its lateral extension scale.

[0140] exist Figure 5C In, similar to Figure 5AA non-diffractive laser beam with a non-radial-symmetric transverse intensity distribution is illustrated. Specifically, this transverse intensity distribution is stretched and nearly elliptical in the y-direction. Figure 5D The image shows the longitudinal intensity distribution of the laser beam 20, where the focusing region 220 again has an extension dimension of L = 3 mm. Figure 5E It shows Figure 5C The magnified local distribution of the lateral intensity shows that different maximum intensities are generated by the superposition of different sub-laser beams 200. In particular, the focusing region 220 is significantly elongated in the horizontal direction A relative to the vertical direction B, where the two directions are perpendicular to each other.

[0141] When a laser beam 20 having such a focusing region 220 is introduced into the workpiece 1, the resulting material modification 5 has the same properties as... Figure 6 The same shape is shown. However, material modification is introduced into material 1 in a superimposed manner, thus producing a uniform material modification surface 50.

[0142] If a laser beam 20 with a circular or non-radially symmetrical transverse intensity distribution is projected onto the surface 10 of the workpiece 1 at an angle of attack α, a distortion in the intensity distribution occurs in the incident plane. This is illustrated in Figure 7. Figure 7A , Figure 7B In this process, a laser beam 20 with a non-radial symmetric transverse intensity distribution is projected onto the surface 10 of the workpiece 1. The minor axis B can, for example, be located in the incident plane, while the major axis A of the beam profile is parallel to the feed direction V. However, since the minor axis B is projected onto the surface 10, its intensity distribution is along the length B / cosα, thus making the minor axis B longer by increasing the angle of attack. In particular, this allows for a situation where the projection of the minor axis B corresponds to the length of the major axis A. From this point onward, the feed rate must be adapted in an unfavorable manner. For example, at an angle of attack of 45°, the minor axis increases to... Therefore, if the ratio A / B before projection is greater than Therefore, during projection, the orientation of the major axis A relative to the dividing line 4 remains unchanged.

[0143] Figure 8 shows another example regarding the effects of projection. Figure 8A It shows Figure 5A A Bessel-Gauss beam, incident perpendicularly on the surface 10 of workpiece 1. For example... Figure 8B As shown, when the angle of attack α is non-zero, the radially symmetrical intensity distribution on the surface 10 of workpiece 1 changes to an elongated intensity distribution along one direction, thereby giving the resulting material modification 5 a preferred direction. The preferred direction of the material modification 5 can be adjusted or changed accordingly by projecting the laser beam 20 onto the surface 10 of workpiece 1. Figure 8C It shows Figure 5CThe Bessel beam. Through projection onto surface 10 of workpiece 1, the orientation of the major axis A remains unchanged, such that the orientation of the preferred direction of crack propagation in the resulting material modification 5 does not change. A / B here is less than the reciprocal of the cosine of the angle of attack α.

[0144] The laser beam 20 can be polarized, preferably parallel to the incident plane, to minimize reflection loss. Therefore, in Figure 9 The figure shows the transmittance of laser radiation through workpiece 1 under polarization conditions parallel and perpendicular to the incident plane, according to Fresnel's formula. Here, the angle of attack α is shown particularly on the X-axis; however, according to... Figure 4A The sub-laser beam 20 has a convergence angle α' relative to the optical axis 30.

[0145] For example, at an angle of attack α = 50° and a convergence angle α' = 20°, the sub-laser beam 200 is incident on the surface 10 of the workpiece 1 within an angle range of α-α' = 30° to α+α' = 70°. Consequently, the transmittance fluctuates between 96% and 94% when incident perpendicularly, and varies between 95% and 70% when incident perpendicularly. Therefore, the variation for the laser beam 200 polarized perpendicular to the incident plane is significantly stronger than that for light polarized parallel to the incident plane. Therefore, it is particularly advantageous, in order to reduce reflection loss, for the sub-laser beam 200 to strike the workpiece 1 at an angle less than 80° relative to the surface normal N.

[0146] exist Figure 10 An embodiment of the apparatus for performing this method is shown. Here, a laser pulse is provided by an ultrashort pulse laser 2 and deflected by a beamforming optical system 34 via a polarizing optical system 32. The laser beam 20 is deflected onto the workpiece 1 by the beamforming optical system 34 via a telescope system 36, wherein the optical axis 30 of the processing optical system 3 is oriented at an angle α relative to the surface normal N of the workpiece 1.

[0147] Here, the polarizing apparatus 32 may include a polarizer that polarizes the laser beam 20 emitted by the ultrashort pulse laser 2, such that the polarizer has only a clearly defined polarization. The subsequent λ / 2 plate can then finally rotate the polarization of the laser beam 20, so that the laser beam 20 can be introduced into the workpiece 1 preferably in a polarized manner parallel to the incident plane.

[0148] In the example shown, the beamforming optics 34 is an axial conical mirror to shape the incident laser beam 20 into a non-diffractive laser beam. However, the axial conical mirror can also be replaced by other elements to produce a non-diffractive beam. The axial conical mirror produces a tapered laser beam 20 from a preferably collimated input beam. Here, the beamforming optics 34 can also give the incident laser beam 20 a non-radially symmetrical intensity distribution. The laser beam 20 can finally be imaged onto the workpiece 1 by a telescope optics 36, which is composed of two lenses 360, 362, wherein the imaging can be magnified or reduced. Components of the telescope optics 36, especially lens 360, can also be integrated into the beamforming optics 34. An axial conical mirror with a refractive freeform surface or a spherically ground backside can, for example, have the lens function of lens 360 and the beamforming function of beamforming optics 34.

[0149] Figure 11A The feed device 6 is shown, configured to move the machining fixture 3 and the workpiece 1 translationally along three spatial axes and rotate about two spatial axes. The laser beam 20 of the ultrashort pulse laser 2 is deflected onto the workpiece 1 by the machining fixture 3. Here, the workpiece 1 is arranged on the placement surface of the feed device 6, wherein the placement surface preferably neither reflects laser energy not absorbed by the material nor strongly scatters it back into the workpiece 1.

[0150] The laser beam 20 can be coupled into the processing optical tool 3, in particular, via a beam guiding device 38. Here, the beam guiding device can be a free-space path with a lens and mirror system, such as... Figure 11A As shown. However, the beam guiding device 38 can also be a hollow fiber with an input optical system and an output optical system, such as... Figure 11B As shown.

[0151] exist Figure 11A In the current example, the laser beam 20 is deflected toward the workpiece 1 by a mirror structure and introduced into the workpiece 1 from the machining fixture 3. The laser beam 20 causes material modification 5 in the workpiece 1. The machining fixture 3 can move and be adapted relative to the material with the feed device 6 such that, for example, a preferred direction or axis of symmetry of the lateral intensity distribution of the laser beam 20 can be adapted to the feed trajectory and thus the dividing line 4.

[0152] Here, the feeding device 6 can move the workpiece 1 at a feed rate V under the laser beam 20, so that the laser beam 20 introduces material modification 5 along the desired dividing line 4. In the illustrated... Figure 11AIn particular, the feeding device 6 includes a first axis system 60, which allows the workpiece 1 to be moved along the XYZ axes and rotated if necessary. The feeding device 6 may also have a workpiece holder 62 configured to hold the workpiece 1. If necessary, the workpiece holder may also have degrees of freedom of movement, such that the long axis of the non-radially symmetrical transverse intensity distribution can be oriented perpendicular to the beam propagation direction and always tangential to the desired dividing line 4.

[0153] For this purpose, the feeding device 6 can also be connected to a regulating electronics 64, which translates user commands from the device user into control commands for the feeding device 6. A predetermined cross-sectional pattern can be stored in the memory of the regulating electronics 64, and the process can be automatically controlled by the regulating electronics 64.

[0154] The regulating electronics 64 can also be connected to the ultrashort pulse laser 2. Here, the regulating electronics 64 can request or trigger the emission of laser pulses or laser pulse sequences. The regulating electronics 64 can also be connected to other components mentioned above and thus coordinate material processing.

[0155] Therefore, pulse triggering in a position-controlled manner can be achieved, for example, by reading the shaft encoder 600 of the feed device 6 and interpreting the shaft encoder signal as position information by the regulating electronics 64. Thus, it is possible for the regulating electronics 64 to automatically trigger the emission of a laser pulse or laser pulse sequence when, for example, an internal adder that sums the distances traveled reaches a certain value and is then reset to 0. Therefore, for example, laser pulses or laser pulse sequences can be automatically emitted into the workpiece 1 at regular intervals.

[0156] Since the feed speed V and feed direction, as well as the dividing line 4, can also be processed in the regulating electronics 64, laser pulses or laser pulse sequences can be emitted automatically.

[0157] The regulating electronics 64 can also calculate the spacing or position of the laser pulse beam or laser pulse sequence to be emitted based on the measured velocity and the fundamental frequency provided by the laser 2. This, in particular, enables the material modification 5 to form a material modification surface 50 that is as uniform as possible.

[0158] Because laser pulses or pulse sequences are emitted in a position-controlled manner, there is no need for complex programming of the segmentation process. Furthermore, freely selectable process speeds can be easily achieved.

[0159] exist Figure 11CThe same also shows the feeding device 6, in which the machining fixture is guided on the workpiece 1 by a 5-axis arm to introduce the material modification 5 into the workpiece 1. The combination of rotating arms allows the machining fixture to move along three spatial axes and rotate about two spatial axes.

[0160] Where applicable, all individual features shown in the embodiments may be combined and / or interchanged with each other without departing from the scope of the invention.

[0161] List of reference numerals

[0162] 1. Workpiece 1' Block-shaped workpiece

[0163] 10 Surface 11 Upper side

[0164] 110 edge

[0165] Section 12, Lower Side

[0166] 130 Edges 14 Shaped edges, chamfers, bevels

[0167] 2. Ultrashort pulse laser with 20 laser beams

[0168] 200 sub-laser beams, 220 focal area

[0169] 3. Machining optical tools with a 30mm optical axis

[0170] 32 Polarizing optical apparatus; 34 Beamforming optical apparatus

[0171] 36 Telescope; 38 Beam guiding equipment

[0172] 360 First lens 362 Second lens

[0173] 4. Dividing line 40. Chemical bath.

[0174] 42 Heating Plate

[0175] 5. Material Modification

[0176] 50 Material Modification Surface

[0177] 6. Feeding equipment

[0178] 60-axis equipment

[0179] 62 Workpiece Holder

[0180] 64. Adjustment electronic device

[0181] α Angle of attack

[0182] β angle of refraction

[0183] A First Axis

[0184] B Second Axis

[0185] N Surface Normal

[0186] V feed

[0187] H hypotenuse

Claims

1. A method for dividing a workpiece having a transparent material, wherein, Material modification (5) is introduced into the transparent material of the workpiece along the dividing line (4) using an ultrashort laser pulse from an ultrashort laser (2), and then the material of the workpiece is divided along the resulting material modification surface (50) using a dividing step. Its features are, The laser pulse arrives at the workpiece at an angle of attack (α), the material modification (5) is a type I and / or type II modification associated with the refractive index change of the material of the workpiece, the material modification (5) penetrates the two sides of the workpiece located in the intersecting plane, a chamfer and / or a bevel is generated by the segmentation step and the size of the bevel and / or the bevel's hypotenuse (H) is between 50 µm and 500 µm, the laser beam (20) formed by the ultrashort laser pulse is a non-diffractive laser beam and has a non-radially symmetric transverse intensity distribution (220), wherein the transverse intensity distribution (220) is elongated on the first axis (A) compared to the second axis (B), wherein the second axis (B) is perpendicular to the first axis (A), and the projection of the non-radially symmetric transverse intensity distribution (220) on the material is elongated in the feed direction (V).

2. The method according to claim 1, characterized in that, The material modification is introduced through the accumulation of heat in the material.

3. The method according to any one of the preceding claims, characterized in that, The segmentation step includes mechanical segmentation and / or chemical segmentation steps and / or thermal application.

4. The method according to claim 1 or 2, characterized in that, The size of the chamfer and / or the bevel (H) is between 100 µm and 200 µm.

5. The method according to claim 1 or 2, characterized in that, The pulse energy of the laser pulse is between 10 µJ and 5 mJ; and / or The average laser power is between 1 W and 1 kW; and / or The laser pulse is a single laser pulse or part of a laser burst, wherein a laser burst comprises 2 to 20 laser pulses, and the laser pulses of the laser burst have a time interval of 10 ns to 40 ns; and / or The wavelength of the laser is between 300 nm and 1500 nm.

6. The method according to claim 1 or 2, characterized in that, In the first method step, a material modification (5) is introduced into the material, the material modification extending parallel to the surface normal (N) of the material; In the second method step, a material modification (5) is introduced into the material, the material modification extending at an angle relative to the surface normal (N) of the material. The material modification surface (50) of the second method step intersects with the material modification surface (50) of the first method step. The segmentation step is performed after the second method step.

7. The method according to claim 1 or 2, characterized in that, The incident laser beam (20) is polarized parallel to the incident plane.

8. The method according to claim 3, characterized in that, The segmentation step includes an etching process.

9. The method according to claim 5, characterized in that, The laser pulses of the laser burst have a time interval of 20 ns.

10. The method according to claim 5, characterized in that, The wavelength of the laser is 1030nm.

11. An apparatus for dividing a workpiece comprising a transparent material by the method of any one of claims 1 to 10, the apparatus comprising: An ultrashort pulse laser (2), the ultrashort pulse laser being configured to provide ultrashort laser pulses; A processing optical fixture (3) configured to introduce the laser pulses into the material of the workpiece; and a feeding device (6) configured to move the laser beam (20) consisting of the laser pulses and the workpiece relative to each other along a dividing line (4) with a feed (V) and to orient the optical axis (30) of the processing optical fixture (3) at an angle of attack (α) relative to the surface (10) of the workpiece. Its features are, The laser pulse is introduced into the workpiece at an angle of attack (α), the material modification (5) is a type I and / or type II modification associated with a change in the refractive index of the material of the workpiece, the material modification (5) penetrates the two sides of the workpiece located in the intersecting plane, a chamfer and / or a bevel is produced by the segmentation step and the size of the bevel (H) of the chamfer and / or the bevel is between 50 µm and 500 µm, the laser beam (20) is a non-diffractive laser beam and has a non-radially symmetric transverse intensity distribution (220), wherein the transverse intensity distribution (220) is elongated on the first axis (A) compared to the second axis (B), wherein the second axis (B) is perpendicular to the first axis (A), and the projection of the non-radially symmetric transverse intensity distribution (220) on the material is elongated in the feed direction (V).

12. The device according to claim 11, characterized in that, - The processing optical tool (3) includes a telescope system (36) configured to reduce and / or magnify the laser beam (20) and introduce it into the workpiece; and / or - The feed device (6) includes a shaft device (60) and a workpiece holder (62), the shaft device and the workpiece holder being configured to allow the machining tool (3) and the workpiece to move relative to each other in a translating manner along three spatial axes and a rotational manner about at least two spatial axes.

13. The device according to claim 11 or 12, characterized in that, - The angle of attack (α) of the machining fixture (3) is between 0 and 60°; and / or - The sub-laser beam (200) of the laser beam (20) illuminates the workpiece at a maximum angle of attack of 80° relative to the surface normal (N) of the workpiece.

14. The device according to claim 11 or 12, characterized in that, The polarizing apparatus (32) is configured to adjust the polarization phase of the laser beam (20) with respect to the incident plane of the laser beam (20).

15. The device according to claim 11 or 12, characterized in that, - A beam guiding device (38) is configured to guide the laser beam (20) to the workpiece, wherein beam guiding is achieved by means of a mirror system and / or optical fiber; and / or - The regulating electronics (64) are configured to trigger the laser pulse emission of the ultrashort pulse laser (2) based on the relative position of the laser beam (20) and the workpiece.

16. The device according to claim 12, characterized in that, The workpiece holder (62) has a surface that does not reflect and / or scatter the laser beam (20).

17. The device according to claim 14, characterized in that, The polarizing optical tool (32) includes a polarizer and a waveplate.

18. The device according to claim 14, characterized in that, The polarizing device (32) is configured to adjust the polarization phase of the laser beam (20) parallel to the incident plane.

19. The device according to claim 15, characterized in that, The optical fiber is a hollow-core optical fiber.

Images