WO2020254615A1

WO2020254615A1 - Method and device for processing a workpiece with a highly dynamic movement of the laser beam between different spatial regions

Info

Publication number: WO2020254615A1
Application number: PCT/EP2020/067163
Authority: WO
Inventors: Malte DR. KUMKAR; Felix Zimmermann
Original assignee: Trumpf Laser- Und Systemtechnik Gmbh
Priority date: 2019-06-21
Filing date: 2020-06-19
Publication date: 2020-12-24
Also published as: DE102019116803A1

Abstract

The invention relates to a method for processing at least one workpiece (110, 120). The workpiece (110, 120) is supplied with a processing beam (2), preferably a pulsed laser beam, particularly preferably an ultrashort pulse laser beam, wherein the processing beam (2, 2', 2") is moved in a highly dynamic manner between at least two different spatial regions (220, 230) in order to form a processing zone (200).

Description

PROCESS AND DEVICE FOR PROCESSING

A WORKPIECE WITH HIGHLY DYNAMIC MOVEMENT OF THE LASER BEAM BETWEEN DIFFERENT SPATIAL AREAS

Technical area

The present invention relates to a method for machining at least one workpiece with heat-accumulating processes, in particular for welding two workpieces by means of a machining beam, with at least one of the workpieces being transparent to the

Machining beam is. In particular, the invention also relates to the welding of two transparent workpieces such as glasses, ceramics or other crystalline or polymer-based materials using a pulsed laser beam.

State of the art

For laser welding workpieces made of transparent materials and in particular for welding workpieces made of glass or ceramics, it is known to use pulsed lasers and in particular ultrashort pulse lasers. The pulsed laser beam is focused in, on or below a workpiece in which, due to the absorption of the laser energy, the material of one or both of the workpieces of a process zone is melted and the gap between the two workpieces is bridged by the melt, so that in this way after the material has solidified again, a weld seam between the two

Workpieces is formed without a further use of material would be necessary. In other words, welding takes place using the materials already present in the workpieces.

Due to the transparency of at least one, both or all of the workpieces for the

In the machining beam, welding can also be achieved in an area between the workpieces resting against one another. The machining beam is focused through one of the transparent workpieces between the workpieces, so that a

Melting of the material can be achieved at the interface between the workpieces.

When welding transparent materials to one another, it can be due to the in the

Page 1 of 31 The energy introduced into the process zone and the associated high temperatures within the material lead to tensions and / or cracks, which can reduce the quality of the joined materials, at least in the area of the weld seam.

It is therefore known to iteratively optimize laser welding processes for joining transparent materials, with different processing parameters such as the pulse duration and / or the pulse energy of the pulsed laser beam and / or the relative

Feed rate between the process zone or processing beam and the workpieces can be varied in a subsequent quality control, for example by means of a microscope through microscopic examinations of the welds and the other areas of the joined workpieces after the actual

Welding process to determine the quality level and then the appropriate

Iteratively optimize process parameters by varying them.

The processing beam is focused by appropriate optics and the associated beam shaping in the material of one of the workpieces, in both workpieces and / or in the area of an interface between the two adjacent workpieces, with the position and shape of the focus formed in this way Can be part of the optimization process.

One challenge in optimization is to reduce the stresses induced by the laser beam in the joint partners, which can prevent a stable connection between the joint partners.

Other laser machining processes based on heat accumulation such as the modification of workpiece surfaces or volumes as well as laser lift-off processes are also confronted with the problem of the stresses induced in the workpiece by the laser beam.

Presentation of the invention

Based on the prior art, it is an object of the present invention to provide a method and a device for performing the method for machining at least one workpiece, the method and the device intended to further improve the quality of the machined workpiece or the machined workpieces.

This object is achieved by a method with the features of claim 1. Advantageous further developments emerge from the dependent claims, the present description and the attached figures. Accordingly, a method for processing at least one workpiece is proposed, the workpiece being acted upon by a processing beam, preferably a pulsed laser beam, particularly preferably an ultrashort pulse laser beam, the

Processing beam to form a process zone is moved highly dynamically between at least two different spatial areas.

Due to the highly dynamic movement of the processing beam in at least two spatial areas of the process zone, it is possible to distribute the energy of the processing beam over a larger area or a larger volume of the material of the workpiece in order to prevent the occurrence of high temperature stresses in the material of the workpiece to reduce or distribute them and to achieve a more efficient processing of the material.

The purely local entry of thermal energy in a single focus into the material of the workpiece, known from the prior art, is thus distributed in a highly dynamic manner to a larger volume and / or a larger surface using the proposed method.

In the present case, a process zone is a limited volume of material in the workpiece

or a limited material volume overlapping at least two workpieces, into which energy is entered by means of the laser pulses of the machining beam. An energy input thus takes place in the material volume forming the process zone, which leads to heat accumulation and thus to a material change in the material volume. The spatial areas into which the processing beam is moved are preferably so far apart that the respective foci do not overlap and therefore the conventional, purely local input of thermal energy is avoided. At the same time, however, the foci are so close to one another that the energy input through the processing beam moving into the different spatial areas leads to an energy accumulation in the

Process zone leads.

In other words, the individual spatial areas are spaced apart from one another, but coupled with one another to such an extent that heat accumulation is achieved.

For example, the volume of material in the process zone can be accumulated by the

Melt the heat input and, after re-solidification, cause a permanent change in the material in the workpiece or in the workpieces.

The process zone can be adjusted accordingly through the positioning of the spatial areas in which the machining beam is moved, can be defined. The process zone can move relative to the workpiece through a relative movement of the laser optics and the workpiece and / or by actively influencing the laser optics. This can be used to form a spatially extending material modification, for example to form a weld seam.

With the proposed method, inter alia, heat diffusion effects in the material of the workpiece or the workpieces can be better taken into account. In other words, the energy introduced into the process zone by means of the processing beam and thus the temperature increase can partially diffuse into the surrounding volumes of the workpiece while the workpiece is being exposed to the processing beam in another of the spatial areas of the process zone, so that the actual through the machining beam introduced focus resulting temperature gradient in the material of the workpiece is weakened and thus the occurrence of temperature stresses can be reduced.

The absorption behavior within the process zone or the melted material volume in the process zone depends on the intensity distribution and of course on the overall average laser energy input. The initial absorption of the laser energy by the material in the process zone initially takes place in the focus of the processing beam moved into the respective spatial area.

The method is based on the knowledge that in the laser processing of transparent materials, for example the welding of workpieces made of glass by means of the

Machining beams, for example pulsed laser beams, by means of which high intensities can be achieved in the respective beam focus, non-linear absorption effects can be achieved in the transparent material. Are appropriate repetition rates for the pulsed

When the processing beam is used, the energy introduced into the separate spatial areas of the process zone by means of the respective pulses accumulates so that the material melts locally due to corresponding heat accumulation effects. As a result, in the vicinity of the geometric focus of the machining beam moved into the respective spatial area, an absorbing plasma initially of the size of the respective one arises

Focus volume.

On the plasma surface which delimits the process zone and in particular in the area of the plasma surface which is in the direction of the respective incident on the plasma

Processing beam is oriented and on which the processing beam impinges, however, occurs increased absorption. The plasma volume can thus continue to absorb energy due to the increased absorption of the machining beam and the resulting energy input into the plasma volume on the plasma surface, so that the volume of the plasma can continue to grow, this increase in the plasma volume being directed mainly along and in the direction of the machining beam towards the beam source. In other words, the plasma can propagate in an elongated shape along the machining beam. From this, an elongated bubble formed by the plasma can be formed.

In this way, an absorption volume can form, which is the original

Can exceed focus volume many times over.

The nonlinear absorption of the machining beam on the plasma can be influenced by the high

Result from electron temperature in the plasma. The electrons can send energy to the

Release atomic cores, which can lead to lattice vibrations and additional heating of the material due to heat accumulation.

The processing beam can preferably act on different spatial areas of the process zone. In this way, the greatest possible exposure to the process zone can be achieved, so that the temperatures occurring in the materials can be locally reduced in the individual foci of the processing beams, but the temperature required for melting the respective material is still generated in the process zone.

The processing beam can preferably impact different spatial areas of the process zone sequentially and / or randomly and / or chaotically. In other words, the foci of the processing beam move through the process zone in such a way that different spatial areas of the process zone are acted upon by one or more processing beams over time. In this way, too high energies can be avoided in a single location, so that the accumulation of voltages can be reduced.

Preferably, a processing beam emanating from a beam source can be moved by means of an acousto-optical deflector and / or divided into at least two separate processing partial beams. By using an acousto-optic deflector, the processing beam can be divided and deflected with high dynamics and any sequence, so that excessive energies can be avoided in a single location, so that the accumulation of voltages is reduced can. Particularly preferably, the acousto-optic deflector can be acted upon by a sequentially and / or randomly and / or chaotically varying sound wave. In this way, the different spatial areas in the process zone can be acted upon in such a way that excessive energies can be avoided at a single location, so that the accumulation of voltages can be reduced.

Particularly preferably, two acousto-optical deflectors rotated by 90 ° relative to one another can be provided, by means of which the processing beam is deflected in a plane perpendicular to the processing beam. This allows the processing beams to be introduced into the process zone in a spatially very flexible manner.

The processing beam can preferably be shaped by means of a beam shaper before it acts on the different spatial areas. This allows an advantageous

Achieve beam shape by means of which the accumulation of stresses in the material of the workpieces can be reduced

A highly dynamic movement of the processing beam is understood here, inter alia, as one in which the processing beam is moved between the respective spatial areas of the process zone at a frequency of at least 100 kHz. In other words, the processing beam acts on the different spatial areas of the process zone at the stated frequency. The movement of the machining beam preferably takes place at a frequency of 100 kHz up to 10 MHz.

In an alternative view, a highly dynamic movement of the processing beam is understood to mean, among other things, such a movement in which the movement from one spatial area of the process zone exposed to the processing beam to another spatial area of the process zone exposed to the processing beam takes a maximum of 10 ps. The movement of the processing beam preferably lasts between 10 ps and 0.1 ps from one spatial area to another spatial area of the process zone.

In a further alternative consideration, a highly dynamic movement of the processing beam is particularly advantageously understood here to mean, inter alia, one in which the movement from one spatial area of the process zone to which the processing beam is applied to another spatial area of the process zone is made possible, that initially at least one laser pulse, preferably a predetermined pulse train and / or all laser pulses of a burst, is / are introduced into the material of the workpiece in an area of the process zone, then the machining beam is introduced into the workpiece in a highly dynamic manner next spatial area of the process zone is moved and then a further laser pulse, preferably a predetermined further pulse train and / or all laser pulses of a further burst is introduced into the material of the workpiece in this spatial area of the process zone.

In other words, through the highly dynamic movement of the processing beam, laser pulses, preferably the laser pulses of a predetermined pulse train and / or all laser pulses from bursts, can be introduced one after the other in a defined manner into the different spatial areas of the process zone.

The movement of the processing beam is thus preferably interrupted until the laser pulse, preferably the predetermined pulse train and / or the laser pulses of a burst have been introduced into the spatial area of the process zone and is only then moved to the next spatial area of the process zone.

In this alternative consideration, the highly dynamic movement of the processing beam is preferably synchronized with the provision of the laser pulses and / or pulse trains and / or bursts, so that the highly dynamic movement of the processing beam only takes place in the pauses between the laser pulses and / or pulse trains and / or bursts.

In this way, the advantageous effects already described above can be achieved, which lead to an improvement in the quality of the machined workpiece and / or the joining process of two or more workpieces with one another.

The frequency of the movement of the highly dynamic processing can also be higher and, for example, above 10 MHz.

The highly dynamic movement of the processing beam between the different spatial areas for processing can, for example, by means of an acousto-optical

Deflector (AOD), preferably by means of two AODs arranged at an angle, preferably perpendicular to one another, and perpendicular to the beam direction, so that rapid movement of the machining beam can be achieved. By using two AODs arranged at an angle or preferably perpendicular to one another, a deflection can be achieved in the (two-dimensional) plane perpendicular to the processing beam, so that the highly dynamic movement of the processing beam takes place over the surface or through the volume of the workpiece or workpieces can. In the

Using only one AOD, movement along a (one-dimensional) line can be achieved. In an alternative embodiment, a movement of the laser beam in one spatial direction can be achieved by means of an AOD and beam shaping or beam splitting can be achieved by means of a second AOD.

In a further alternative embodiment, a first AOD and a second AOD can be used to achieve a beam deflection in two spatial directions and one or two further AODs to achieve a beam splitting in one or two directions.

The movement of the processing beam and / or its shaping can also be achieved by means of an SLM (spatial light modulator) or diffractive optics.

By means of the highly dynamic movement of the processing beam, the individual spatial areas can be exposed to the processing beam in a predetermined sequence. In other words, a predetermined pattern of spatial areas can be traversed with the machining beam in a highly dynamic manner. The spatial areas can also be scanned in a highly dynamic manner with a chaotic or random pattern.

The individual spatial areas of the process zone can be arranged offset from one another by 1–10 μm, for example. In other words, after each laser pulse or each laser pulse train or each burst, the processing beam can be offset from one another by 1 - 10 pm within the process zone in order to then apply the next laser pulse or the next laser pulse train or the next burst.

The workpieces can be processed, for example, in the form of joining, in particular welding, the workpieces to one another. By introducing the machining beam into the process zone, the material of the work piece (s) is / are melted and a weld seam is formed accordingly after the material has solidified again.

The proposed method can also be used to introduce further modifications to the surface of the material of the workpiece or of the workpieces.

A method for welding at least two workpieces is preferably proposed, at least one of the workpieces being transparent for a machining beam, preferably for a pulsed laser beam, particularly preferably for an ultrashort pulse laser beam, with a process zone in the workpieces in a process zone exposed to the machining beam

Weld seam is formed. Because the processing beam acts on different spatial areas of the process zone, it is possible to provide a distribution of the intensity of the introduced laser energy within the process zone so that the stresses induced by the processing beam in the material of the workpieces can be reduced or at least redistributed to such an extent that a Improvement in the quality of the joined workpieces can be achieved and a large process zone can form.

In this way, several absorption areas can be addressed in the process zone by means of the processing beam, so that a more targeted initiation or guidance of the temperature induced by the processing beam and thus the respective melted areas can be achieved.

In conventional joining methods, a weld seam is made linearly and continuously, so that along this modification introduced by laser-induced melting areas, the temperature-induced stresses also accumulate in the materials of the joint partners. According to the proposed method, the accumulation of the temperature-induced stresses can be reduced by the exposure of different spatial areas of the process zone by the machining beam moved into the different spatial areas, since the temperature input does not take place continuously, but through the

Exposure to the different spatial areas is interrupted.

In other words, the temperature required for melting the material in the process zone is not introduced into the material starting from a single focus, but rather in spatial areas within the process zone which are spatially separated from one another and which are nevertheless thermally coupled to one another to the extent that heat can accumulate in the material.

The highly dynamic deflection of the processing beam, which acts on different spatial areas of the process zone and accordingly leads to spatially separated absorption areas within the process zone, which nevertheless influence each other thermally, the accumulated stresses occurring in the material of the workpieces can be reduced or these spatially be distributed in such a way that their influence on the stability of the joint is reduced. This can prevent the occurrence of

Machining beam induced tensions in the joining partners can be reduced and thus an increased strength of the joint can be achieved.

Furthermore, it is also possible to weld with higher energies compared to conventional methods as the stresses in the material do not accumulate as much. In this way the throughput can also be increased.

By applying the highly dynamic processing beam to different spatial areas of the process zone, the laser-induced heat that is introduced into the material can be individually adapted to the materials of the joining partners and to the other process parameters such as the geometry of the weld seam to be produced.

The process zone acted upon by the machining beam and the workpieces can preferably be moved relative to one another to form the weld seam. Applying a relative movement of the process zone with respect to the workpiece during the welding process results in a weld seam extending in the direction of movement after the previously melted material has solidified.

The machining beam is preferably divided into at least two separate machining partial beams and at least two machining partial beams are then applied in each case

different spatial areas of the process zone.

The processing partial beams can, as described above for the (individual) processing beam, also be moved highly dynamically into different spatial areas of the process zone.

The application of the different spatial areas of the process zone can then take place in a correspondingly highly dynamic manner.

In other words, a highly dynamic movement of the at least two

Processing partial beams take place, so that in each case at least two different spatial areas of the process zone are acted upon simultaneously with the processing partial beams and then, for example, after the two spatial areas have been exposed to one

Laser pulse or a laser pulse train or a burst, the partial processing beams are moved in a highly dynamic manner and correspondingly at least two further spatial areas of the process zone are exposed to the partial processing beams.

The above object is also achieved by a device with the features of

independent device claim solved. Advantageous further developments emerge from the related subclaims, the present description and the attached figures. Accordingly, a device for machining at least one workpiece is proposed, a beam source for providing a machining beam, preferably a pulsed laser beam, particularly preferably an ultrashort pulse laser beam, and an optical system for applying the machining beam to at least one workpiece, the optical system being designed for this purpose and is set up to move the machining beam in a highly dynamic manner between at least two different spatial areas of the at least one workpiece to form a process zone.

The advantageous effects mentioned above for the method can be achieved by means of the proposed device.

The configurations described above with regard to the method can also be used in FIG

Device are included in their respective device-like form in order to achieve the advantages described for the method and to develop the device.

Brief description of the figures

Preferred further embodiments of the invention are illustrated by the following

Description of the figures explained in more detail. Show:

FIG. 1 shows a schematic representation of a section of a device for machining a workpiece in a first exemplary embodiment;

FIG. 2 shows a schematic representation of the application of different spatial areas of a process zone by means of laser pulses;

FIG. 3 shows a schematic representation of a section of a device for carrying out a method for welding two workpieces in another

Embodiment; and

FIG. 4 shows a schematic representation of a section of a device for carrying out a method for welding two workpieces in another

Embodiment.

Detailed description of preferred exemplary embodiments

Preferred exemplary embodiments are described below with reference to the figures. The same, similar or identically acting elements are included in the different figures Provided with identical reference numerals, and a repeated description of these elements is partially omitted in order to avoid redundancies.

In FIG. 1, a section of a device 1 for machining a workpiece, here for machining two workpieces 110, 120, is shown schematically. The device 1 is used for

Carrying out a method for machining the workpieces 110, 120, wherein the machining can be, for example, a modification of the surface of the workpiece or a lift-off method. The proposed method can also be used to introduce further modifications into the material of the workpiece or the material of the workpieces 110, 120.

Machining is preferably provided for welding at least two workpieces 110, 120.

A machining beam 2 is provided by a beam source (not shown here), the beam source preferably being provided in the form of a pulsed laser, preferably an ultra-short pulsed laser.

The parameters of the beam source and the downstream optics can be selected as follows, for example:

- Wavelength between 200 nm and 5000 nm

- Repetition rate between 100 Hz and 50 MHz (optional bursts where the repetition rate of the pulses in the burst can be between 1 MHz and 50 GHz)

- Laser pulse duration between 10 fs and 50 ps

- Focusing so that fluence in the respective spatial areas> 0.01 J / cm2

(Modification threshold in volume typically between 1-5 J / cmz)

- Relative advance of the work piece (s) to the machining beam between 0.01 and 1000 mm / s

The processing beam 2 emanating from the corresponding beam source, not shown, for example in the form of the said pulsed laser, is used in the device 1 for performing the processing of the material of the workpiece 110 or the workpieces 110, 120 in a first optical element 30, which in the embodiment shown as Lens 30 is symbolized, processed so that an acousto-optic deflector 32 following in the beam path can be operated in a suitable manner. The first optical element 30 can accordingly provide beam expansion, collimation, focusing, spatial and / or temporal beam shaping, etc., which is suitable for processing the processing beam 2 in such a way that the acousto-optical deflector 32 can be operated appropriately.

An acousto-optic deflector, which in the exemplary embodiment shown in FIG. 1 is shown very schematically as an acousto-optic deflector 32 combined from two individual acousto-optic deflectors 320, 322, is understood in the present case to mean an active optical element in which by the introduction of sound waves, a deflection of an incoming machining beam can be achieved. An acousto-optic deflector is also known as an AOD.

An acousto-optic deflector can be provided, for example, in the form of a transparent crystal cuboid, for example in the form of quartz glass or another crystal, into which structure-borne sound is entered by means of an acoustic coupler, for example by means of a piezo crystal. Due to the density fluctuations formed in the transparent cuboid by the structure-borne sound, an optical grating is formed correspondingly, on which diffraction of the incident light takes place.

In other words, in the acousto-optic deflector 32, the light can be diffracted at the optical grating formed in the crystal by the sound waves generated by the density fluctuations.

The actual deflection of the incident light or the diffraction of the incident light of the processing beam emanating from the beam source is therefore dependent on the frequency of the acoustic oscillation introduced into the acousto-optical deflector 32 or on the wavelength of the acoustic wave and thus on the one formed in this way Lattice constants of the density fluctuations formed in the cuboid. By varying the introduced frequency of the introduced acoustic oscillation and thus the lattice constant, the actual deflection of the incident light beam of the processing beam can be varied accordingly.

Via the amplitude of the acoustic signals introduced into the acousto-optical deflector 32

Oscillation, on the other hand, can also be achieved with an intensity modulation in such a way that, with a higher amplitude, the corresponding density fluctuations are more pronounced and thus the diffraction orders are more pronounced. In other words, both a variable angular deflection of the light beam and a variation of the intensity of the individual diffraction orders can be achieved in the acousto-optical deflector 32 via the input of sound energy.

According to the exemplary embodiment in FIG. 1, the acousto-optic deflector 32 (or the combination of the two acousto-optic deflectors 320, 322) is arranged correspondingly after the first optical element 30. The processed by the first optical element 30

Processing beam 2 is thus deflected by the acousto-optic deflector 32 or the two acousto-optic deflectors 320, 322 in accordance with the respective settings and in particular the introduced frequency and the introduced amplitude.

A processing beam 2 deflected by a first setting of the acousto-optic deflector 32 and one deflected by a different setting of the acousto-optic deflector 32

Processing beam 2 ″ are shown schematically in FIG. 1 for each of the first diffraction orders. Those in higher diffraction orders are not shown in the figure for the sake of simplicity.

The two deflected processing beams 2 ′, 2 ″ in FIG. 1 thus symbolize two of the many deflections possible by the acousto-optical detector 32, each of which moves one after the other into a spatial area 220, 222 of the process zone 200 into the material of the workpieces 1 10, 120 be introduced. By introducing other frequencies into the AOD (s) 32, other deflections can of course also be achieved, so that other spatial areas of the process zone 200 can also be exposed to the then deflected processing beam.

The movement of the deflected processing beams 2, 2 ″ in such a way that they are introduced into the different spatial areas 220, 230 of the process zone 200 can take place in a highly dynamic manner. This can be done particularly well by means of the acousto-optical deflector 32

(or the two acousto-optic deflectors 320, 322 connected one after the other), since these components enable movement at particularly high frequencies. A distinction must be made here between the (excitation) frequency of the acoustic wave, which takes over the grid formation in the acousto-optical deflector 32, and the frequency of movement of the processing beam. The frequency of the movement of the machining beam corresponds to a frequency of the change in the excitation frequency, i.e. a frequency of the

Switching from one excitation frequency to a subsequent excitation frequency.

A highly dynamic movement of the machining beam, for example by means of one or more AODs 32, 320, 322 is understood to mean, inter alia, one in which the deflected processing beam is moved between the respective spatial areas of the process zone with a frequency of at least 100 kHz (the

Excitation frequency of an AOD with this frequency). The movement of the deflected machining beam preferably takes place at a frequency of 100 kHz up to 10 MHz. A movement of the deflected processing beam can thus be achieved via a corresponding control of the AOD (s) 32, 320, 322 with the frequencies mentioned.

The movement from one spatial area 220 of the process zone 200 acted upon by the deflected processing beam 2 to another spatial area 230 of the process zone 200 acted upon by the deflected machining beam 2 ″ preferably lasts at most 10 ps.

In other words, the change in the excitation frequency of the AOD 32 lasts at most 10 ps. The movement of the deflected processing beam 2 ‘, 2 ″ between 10 ps and 0.1 ps from one spatial area 220 to another spatial area 230 of the process zone 200 is particularly preferred.

The acousto-optic deflector 32 shown in FIG. 1 is accordingly constructed in two parts and two acousto-optic deflectors 320, 322 arranged one after the other in the beam path are provided, which are rotated 90 ° to each other in the embodiment shown in order to deflect of the machining beam 2 in the plane lying perpendicular to the machining beam 2 (ie an X / Y plane). Of course, the two acousto-optic deflectors 32 can also be oriented at a different angle to one another - however, the 90 ° orientation enables easier control, the deflection then taking place in accordance with the desired X / Y deflection.

The acousto-optical using the composed of the individual AODs 320, 3220

Deflector 32 deflected machining beams 2 ‘, 2 ″ are prepared for further processing by means of a second optical element 34, which in the embodiment shown is also shown schematically in the form of a lens. For example, the

Processing beams 2 ‘, 2 ″ are collimated by means of the second optical element 34 for propagation into the far field.

The second optical element 34 can accordingly achieve, for example, a collimation of the processing beams 2, 2 ″ emanating from the acousto-optical deflector 32.

In such an arrangement of two acousto-optic detectors, a half-wave plate is preferably provided between the two acousto-optic deflectors. Since in the acousto-optical deflector 32 there is no complete decoupling of the incoming processing beam 2 exclusively into the processing beam 2, '2' separated by the respective diffraction angle of the first diffraction order, but also in the zeroth

Diffraction order, that is to say collinear with the processing beam 2 arriving from the beam source, and a beam intensity is also still present, a diaphragm 36 is provided to eliminate the zeroth diffraction order. The aperture 36 can also serve to raise rays in higher

Eliminate diffraction orders to ensure a clean decoupling of only the first

To achieve diffraction order.

In other words, a jet cleaning element is introduced into the beam path through the diaphragm 36, by means of which undesired components can be removed from the jet.

By means of a third optical element 38 arranged in the beam path after the second optical element 34 and the diaphragm 36, which is also shown in the form of a lens in FIG. 1, one spacing from the zeroth diffraction order is then established

having machining beams 2 ‘, 2 ″, ie having a spatial offset, are focussed again. In other words, the third optical element 38 achieves a focusing of the machining beams 2 ″, 2 ″ provided with a local offset into the material of the workpiece 110, 120 or into the process zone 200 located in the workpieces 110, 120.

By using the acousto-optical deflector 32, a very rapid movement of the processing beam 2 ‘, 2 ″ can be achieved, with the processing beam 2‘, 2 ″ then being able to be introduced into different spatial areas 220, 230 of the process zone 200.

In FIG. 2, the application of laser pulses 250 to different spatial areas 220, 230 of the process zone 200 is shown in a very schematic diagram. The laser pulses 250 are combined very schematically in the diagram to form bursts 252 that are separate from one another. The bursts 252 each last a period of time TB.

In FIG. 2, a burst 252 is introduced into a different spatial area 220, 230, 240 of the process zone 200. The individual bursts 252 are introduced one after the other into the different spatial areas 220, 230, 240.

In the pauses TP between the bursts 252, the processing beam is deflected by a corresponding control of an AOD 32 so that successive bursts 252 in

different spatial areas 220, 230, 240 are introduced into the workpiece. The bursts 252 of the processing beam 2 and the control of the AODs are preferably synchronized with one another such that a change in the excitation frequency of the AODs takes place in the respective pulse pauses TP between the bursts 252. The new

The excitation frequency is set for the AODs and only then is a laser pulse or a burst or a pulse train sent through the AODs.

In other words, through the highly dynamic movement of the processing beam, laser pulses, preferably the laser pulses of a predetermined pulse train and / or all laser pulses from bursts, can be introduced one after the other in a defined manner into the different spatial areas 220, 230, 240 of the process zone 200.

The movement of the processing beam is thus preferably interrupted until the laser pulse, preferably the predetermined pulse train and / or the laser pulses of a burst have been introduced into the spatial area 220 of the process zone 200 being formed and only then becomes the next spatial area 230 of the process zone 200 emotional.

FIG. 3 schematically shows a section of a device 1 for carrying out a method for welding two workpieces 110, 120, likewise shown schematically, by means of a machining beam 2.

The workpieces 1 10, 120 can be transparent workpieces, with at least the workpiece 1 10 lying on top in the beam direction having to be transparent to the machining beam if welding is to be carried out at an interface 100 between the upper workpiece 110 and the lower workpiece 120 .

The actual weld is shown here schematically in the form of a weld seam 210, which in the exemplary embodiment shown has an essentially linear and continuous extension. However, differently shaped weld seams for joining the workpieces 110, 120 are also conceivable, for example in a curved or curved shape or through the formation of individual segments or weld points.

Herein, a transparent workpiece is understood to mean one that is suitable for the

Processing beam 2 is transparent. In other words, the machining beam 2 can pass through a transparent workpiece without significant weakening or scattering.

The position of a weld seam 210 generated between the workpieces 110, 120 by means of the machining beam 2 and the structure of the device 1 or 3 for performing the method for welding the workpieces 220, 230 are detailed again with reference to FIG shown.

In FIG. 3, a processing beam 2 is shown schematically, which emanates from a beam source not shown in the figure and which can be provided in the form of a pulsed laser beam. An ultrashort pulse laser can particularly preferably be used to provide the machining beam 2.

For example, a pulsed laser beam with wavelengths of 1030 nm or 1064 nm or 515 nm or 532 nm with pulses in the femtosecond range or picosecond range and with frequencies of the repetition rate of 100 kHz up to several MHz can be used. The laser for generating the pulsed laser beam can also be operated in burst mode.

The processing beam 2 emanating from the beam source, not shown here, for example in the form of the said laser, is processed in the device 1 for performing the welding in a first optical element 30, which is symbolized as lens 30 in the exemplary embodiment shown, so that a beam path subsequent acousto-optic deflector 32 can be operated appropriately. The first optical element 30 can accordingly provide beam expansion, collimation, focusing, beam shaping in the time domain, etc., which is suitable for conditioning the processing beam 2 in such a way that the acousto-optical deflector 32 can be operated appropriately.

An acousto-optic deflector, which is shown very schematically in the exemplary embodiment at reference number 32, is understood in the present case to be an active optical element in which an incoming sound wave is deflected

Machining beam can be achieved. An acousto-optic deflector is also known as an AOD.

In other words, in the acousto-optic deflector 32, the light can be diffracted at the optical grating formed in the crystal by the density fluctuations generated by the sound waves. The actual deflection of the incident light or the diffraction of the incident light of the processing beam emanating from the beam source is therefore dependent on the frequency of the acoustic oscillation introduced into the acousto-optical deflector 32 or on the wavelength of the acoustic wave and thus on the one formed in this way Lattice constants of the density fluctuations formed in the cuboid. By varying the introduced frequency of the introduced acoustic oscillation and thus the lattice constant, the actual deflection of the incident light beam of the processing beam can be varied accordingly.

Oscillation, on the other hand, can also be achieved with an intensity modulation in such a way that, with a higher amplitude, the corresponding density fluctuations are more pronounced and thus the diffraction orders are more pronounced.

In other words, both a variable angular deflection of the light beam and a variation of the intensity of the individual diffraction orders can be achieved in the acousto-optical deflector 32 via the input of sound energy.

According to the exemplary embodiment in FIG. 3, the acousto-optical deflector 32 is arranged correspondingly after the first optical element 30. The processing beam 2 processed by the first optical element 30 is thus deflected by the acousto-optical deflector 32 in FIG

Processing partial beams, which are shown schematically in FIG. 3 in the form of processing partial beams 20, 22 of the first order of diffraction, divided and deflected. The ones in higher

Diffraction orders are not shown.

The processing partial beams 20, 22 deflected by means of the acousto-optical deflector 32 are prepared for further processing by means of a second optical element 34, which in the embodiment shown is also shown schematically in the form of a lens. For example, the processing partial beams 20, 22 can be collimated by means of the second optical element 34 for propagation into the far field.

The second optical element 34 can accordingly achieve, for example, a collimation of the processing partial beams 20, 22 emanating from the acousto-optical deflector 32.

Instead of the one acousto-optic deflector 32 shown in FIG to reach perpendicular to the machining beam 2 plane. Of course, the two acousto-optic deflectors 32 can also be aligned at a different angle to one another - however, the alignment at 90 ° enables easier control.

In such an arrangement of two acousto-optic detectors, a half-wave plate is preferably provided between the two acousto-optic deflectors.

Since in the acousto-optical deflector 32 there is no complete decoupling of the incoming processing beam 2 exclusively into the partial beams 20, 22 separated by the respective diffraction angle of the first diffraction order, but also in the zeroth

Diffraction order, that is to say collinear with the processing beam 2 arriving from the beam source, and a beam intensity is also still present, a diaphragm 36 is provided to eliminate the zeroth diffraction order. The diaphragm 36 can also serve to sub-beams in higher

Eliminate diffraction orders to ensure a clean decoupling of only the first

To achieve diffraction order.

By means of a third optical element 38 arranged in the beam path after the second optical element 34 and the diaphragm 36, which is also shown in the form of a lens in FIG. 3, the one spacing from the zeroth diffraction order is then established

having, that is to say having a spatial offset, machining partial beams 20, 22 are focussed again. In other words, the third optical element 38 achieves a focusing of the partial processing beams 20, 22 provided with a spatial offset.

The processing partial beams 20, 22 are focused on a beam shaper 40, which is provided, for example, in the form of a phase-sensitive element, for example a spatial light modulator (SLM), which is also referred to as a spatial modulator for light. The spatial structure of short laser pulses can be shaped via such an SLM. In particular, it can be used to form laser pulses in Bessel form or in the form of several Gaussian spots.

The beam shaper 40 can also be another active optical element around the

Shape machining beam.

By means of the beam shaper 40, the processing partial beams 20, 22 can be shaped in their beam structure in such a way that they have a predetermined spatial structure, for example. By means of the beam shaper 40, the patterns or structures for the application of the processing beam 2 or the processing partial beams 20, 22 to the different spatial areas of the process zone can also be specified. By means of the beam shaper 40, the processing partial beams 20, 22 can also be divided into further processing partial beams not shown in the schematic exemplary embodiment, or predetermined patterns or patterns can be generated from each of the processing partial beams 20, 22.

After the beam shaper 40, those correspondingly shaped by the beam shaper 40 occur

Processing partial beams then pass through a further optical element 42, which in the exemplary embodiment shown in FIG. 3 is again shown in the form of a lens. By means of the further optical element 42, each of the individual ones is focused

Processing beams, which have either only been split by the acousto-optical deflector 32 or also additionally by the beam shaper 40, take place in the process zone 200 that is being formed.

The individual optical elements 30 to 38, 40 and 42 can be organized in a common optical system 400. With the exception of the acousto-optical deflector 32, all other optical elements are optional.

The forming process zone 200 lies at least partially in one or in both of the

Workpieces 1 10, 120. By focusing the one having a local offset

Processing partial beams 20, 22 into the process zone 200 by means of the further optical element 42, accordingly, a focusing of the processing partial beams 20, 22 in different spatial areas 220, 230 of the process zone 200 takes place. In other words, the one of the processing partial beams 20 is in a first spatial region 220 of the

Process zone 200 is focused, whereas another of the processing partial beams 22 is focused into a second spatial area 230 of the process zone 200.

The spatial area 220 acted upon by the first processing partial beam 20 is at a distance from the spatial area 230 acted upon by the second processing partial beam 22, since the processing partial beams 20, 22 also have a spatial offset from one another. The two areas 220, 230 acted upon by the processing partial beams 20, 22, however, are preferably only spaced so far apart that there is a thermal coupling of the two areas 220, 230. It can thus be achieved that the material present in the process zone 200 of one or both of the workpieces 1 10, 120 by the entry of the

Laser energy is melted by the processing partial beams 20, 22 despite the spatial spacing of the two areas 220, 230.

The device 3 accordingly comprises the optical system 400, through which the pulsed machining beam 2 then in the form of the machining partial beams 20, 22 onto the workpieces 1 10.120. The processing partial beams 20, 22 are focused into the spatial areas 220, 230 in a process zone 200 located in one or both workpieces 110, 120, whereby the intensity of the processing partial beams 20, 22 is highest in the foci located in the process zone 200, In contrast, lower in the respective surrounding areas. The

Material processing in the process zone 200 takes place in that the material present in the process zone 200 melts due to the high intensity of the processing partial beams 20, 22 in their respective foci. As a result, during the subsequent cooling, for example, welding of two material areas that were previously present separately in the process zone 200 and that are now cohesively connected to one another by the melting can be achieved.

When using a pulsed machining beam 2, in particular when using an ultrashort pulse laser, the very high intensities that can be achieved in the foci provided by the optical system 400 in the glass material of the at least one workpiece 1 10, 120 achieve non-linear absorption effects. When using suitable repetition rates of the pulsed machining beam 2, heat accumulation effects occur in the glass material, as a result of which there is a local melting of the glass material in the process zone 200.

The method is based on the knowledge that when welding workpieces 1, 10, 120 made of glass by means of a pulsed machining beam 2, for example a pulsed laser beam, preferably an ultrashort pulse laser, non-linear absorption effects can be achieved in the glass due to the high intensities that can be achieved in the respective beam focus . If corresponding repetition rates are used for the pulsed machining beam, the energy introduced into the process zone 200 by means of the respective pulses accumulates, so that the glass material melts locally due to corresponding heat accumulation effects. This creates the pulsed in the vicinity of the respective geometric focus

Machining partial beams 20, 22 produce a highly absorbent plasma initially in the size of the focus volume.

In order to achieve a connection of the workpieces 110 and 120, the forming process zone 200 is accordingly placed in the workpieces 110, 120 in such a way that it is arranged close to the interface 100 or includes the interface 100. For this purpose, the processing partial beams 20, 22 are processed accordingly by means of the correspondingly designed and set up optical system 400 and are focused into the process zone 200 that is being formed.

The material of one, several or all of the workpieces 110, 120 is then melted in the process zone 200, and then after the renewed solidification of the previously melted Materials to achieve a welding of the workpieces 1 10, 120 through the melted and then solidified material.

The positioning of the individual spatial areas 220, 230 in the process zone 200 can be varied in that different deflections of the processing partial beams 20, 22 in the acousto-optic deflector 32 are achieved by coupling varying sound waves into the acousto-optic deflector 32. Both the frequencies and the intensities of the sound waves coupled into the acousto-optic deflector 32 can be varied.

By means of a corresponding sequence of frequencies coupled into the acousto-optic deflector 32, a corresponding sequence of deflections of the processing partial beams 20, 22 can then be achieved, which in turn occurs in a sequence of different spatial offsets of the processing partial beams, which in turn in a sequence of exposure to different spatial areas 220 , 230 of the process zone 200 results.

This can be coupled into the acousto-optical deflector 32 via the control

Sound waves are achieved that the process zone 200 is acted upon by the processing partial beams 20, 22 in a sequence of different regions 220, 230 that are spaced apart from one another.

In other words, the volume of the process zone 200 can be scanned by means of the acousto-optical deflector 32.

The sequence of the different frequencies coupled into the acousto-optical deflector 32 can consist of a fixed sequence and / or be chaotic and / or random within predetermined limits.

In other words, the acousto-optic deflector 32 functions in the one shown

Embodiment like a scanner, by means of which a division of the processing beam 2 originally emanating from the beam source is made possible into two processing partial beams 20, 22, which are processed accordingly in their beam shape via the subsequent optics and then in spatial areas determined by means of the acousto-optical deflector 32 220, 230 of the process zone 200 impinge. By varying the deflection of the partial beams 20, 22 in the acousto-optical deflector 32, the position of the spatial regions 220, 230 in the process zone 200 can also be varied.

By appropriately designing the acousto-optic deflector 32 and the subsequent ones Optics, in particular the shape of the aperture 36 and the shape of the beam shaper 40, can furthermore be achieved by means of the acousto-optical deflector 32 that the different spatial areas 220, 230 of the process zone 200 are addressed one after the other or sequentially or simultaneously.

The high dynamics of the acousto-optic deflector 32 also enables the respective deflection of the partial beams 20, 22 to be switched quickly such that the spatial areas 220, 230 of the process zone 200 can be shifted quickly or one after the other

different patterns or patterns can be run.

A sequential or chaotic or random or otherwise designed control of the acousto-optical deflector 32 can lead to the fact that, although sufficient energy is introduced into the process zone 200 that is formed, in order to reduce the amount of work required for the melting of the work piece (s) 110, 120 to achieve the necessary temperatures, which leads to a melting of the material, for example at an interface between the workpieces 110, 120.

At the same time, however, the continuous and uninterrupted occurrence of high local temperatures over a period of time that is too long is avoided, so that the entry of temperature-induced stresses into the workpieces 110, 120 and in particular into areas of the workpieces 110, which are adjacent to the process zone 200 or the melting area. 120 is reduced.

The partial machining beams 20, 22 impinging on the workpieces 110, 120 are shown in FIG

Displacement direction X relative to the workpieces 110, 120 to move in the

Workpieces 110, 120 draw in a linear or curved weld seam 210. Either the workpieces 110, 120 or the

Machining partial beams 20, 22 or both are displaced in opposite directions along the displacement direction X. Other movements can also be carried out parallel to the plane formed by the interface 100 in order to draw in correspondingly more complex shapes of weld seams 210. As a result of the movement of the machining partial beams 20, 22 relative to the workpieces 110, 120, the expansion of the weld seam 210 in the

Direction of movement X can be determined.

Since the scan speeds that can be achieved with the acousto-optical deflector 32 are very high, the energy required for reliable melting and thus a reliable connection of the Workpieces can reach each other, but at the same time due to the distributed input of energy and avoidance a continuously linear introduction of the laser energy along the desired weld seam 210, the avoidance of stresses can be achieved.

Because the processing beam 2 originally coming from the beam source is divided into at least two processing partial beams 20, 22 and the processing beam is applied in different spatial areas 220, 230 of the process zone 200, and in particular a dynamic application of the different spatial areas 220, 230 takes place , it can be avoided that the weld seam 210 in the

Joining partner by introducing a continuous, constant and uniform

Heating zone, as it occurs through the introduction of a continuous beam with a laser beam in conventional welding processes, introduces increased stresses. Rather, in the proposed method, the local heating is repeatedly interrupted and shifted to a different spatial area 220, 230 within the process zone 200, so that the

Heat input at a single spot, which coincides with the focus of the processing partial beam 20, 22, is interrupted and accordingly is also not introduced continuously at the one spot.

In other words, the process zone 200 in different spatial areas 220, 230, which change sequentially and / or chaotically and / or randomly over the course of time and along the weld seam to be achieved, is nevertheless supplied with the necessary energy to generate the weld seam.

The distance between the different spatial areas 220, 230 of the process zone 200 is usually selected such that there is a thermal coupling between the different spatial areas 220, 230. It can thus be achieved that the melt required for joining the workpieces 110, 120 is formed in the process zone 200, while a high local energy input along a single, continuous, continuous welding line is avoided.

In FIG. 4, the device and the method for machining two workpieces 1 10, 120 are shown again in a second detailing.

In the embodiment shown, the workpieces 110, 120 are made of glass - for example in the form of two glass panes - which are arranged on a common interface 100 arranged between the two workpieces 110, 120 and are welded to one another at a section of the interface 100 will. In other words, at least part of the underside 114 of the upper workpiece 110 shown in FIG. 3 lies on the Top 122 of lower workpiece 120. The upper side 122 of the lower workpiece 120 and the lower side 114 of the upper workpiece 110 correspondingly together form the interface 100 in which the welding is to be carried out or has been carried out.

The two workpieces 110 and 120 can be pressed together in the area of the formation of the interface 100 in order to achieve a preliminary positioning and fixation of the two workpieces 110 and 120 with respect to one another even before the welding.

Due to the nature of their material, namely glass, the two workpieces 1 10, 120 are essentially transparent to the pulsed machining beam 2 or the

Processing partial beams 20, 22 with which the welding of the two workpieces 1 10, 120 is to be carried out. In this way, the pulsed machining partial beams 20, 22, which are provided for carrying out the welding, can pass through the workpieces 110 and 120 and in particular also through the upper workpiece 110 to the

Get to interface 100. This means that the workpieces 110 and 120 are welded within the joint formed by the two workpieces 110, 120

Workpiece volume possible.

Such a welding within a workpiece volume formed by at least two workpieces is not possible in the case of materials that are opaque to a machining beam.

The lower workpiece 120 can, however, also be designed to be opaque for the machining beam 2 or the machining partial beams 20, 22. However, the processing partial beams 20, 22 can still pass through the upper, for the processing partial beams 20, 22, glass workpiece 110 to the interface 100 between the two workpieces 110, 120 in order to carry out welding.

The structure of the optical system 400 otherwise corresponds to that described for FIG.

As far as applicable, all the individual features that are shown in the exemplary embodiments can be combined with one another and / or exchanged without departing from the scope of the invention. Reference list

1 device for performing welding of workpieces 100 interface

1 10 (above) workpieces

1 12 upper surface of the upper workpiece

1 14 lower surface of the upper workpiece

120 (lower) workpiece

122 upper surface of the lower workpiece

124 lower surface of the lower workpiece

2 machining beam

2 ‘deflected machining beam

2 “deflected machining beam

20 processing partial beam

22 Processing partial beam

200 process zone

210 weld seam

220 spatial area of the process zone

230 spatial area of the process zone

240 spatial area of the process zone

250 laser pulses

252 burst

30 first optical element (lens)

32 acousto-optic deflector

34 second optical element (lens)

36 aperture

38 third optical element (lens)

40 beam shaper

42 further optical element (lens)

400 optical system

X direction of movement

TP break

TB burst

Claims

Expectations

1. A method for machining at least one workpiece (110, 120), the workpiece (110, 120) being acted upon by a machining beam (2), preferably a pulsed laser beam, particularly preferably an ultrashort pulse laser beam, the

Processing beam (2, 2 ‘, 2", 20, 22) to form a process zone (200)

is moved highly dynamically between at least two different spatial areas (220, 230).

2. The method according to claim 1, characterized in that the processing beam (2) is moved between the two spatial areas (220, 230) at a frequency of 100kHz to 10MHz and / or that the processing beam is moved between 10ps to 0.1ps the two spatial areas (220, 230) is moved.

3. The method according to claim 1 or 2, characterized in that the

Processing beam (2) is moved by means of an acousto-optical element (32, 320, 322), preferably by means of two acousto-optical elements which are oriented at an angle to one another.

4. The method according to claim 3, characterized in that the acousto-optical

Element (32) is acted upon by a sequentially and / or randomly and / or chaotically varying sound wave.

5. The method according to any one of the preceding claims, characterized in that the machining beam (2) is a pulsed laser beam and the movement between the two spatial areas (220, 230) is carried out in the pulse pauses (TP).

6. The method according to any one of the preceding claims, characterized in that at least two workpieces (110, 120) are provided, at least one of the workpieces (110, 120) being transparent to the machining beam (2), and in the

Workpieces (1 10, 120) in the process zone (200) a weld seam (210) is formed, wherein the machining beam (2) is highly dynamic in at least two separate

Processing partial beams (20, 22) is divided and at least two

Processing partial beams (20, 22) each act on different spatial areas (220, 230) of the process zone (200) and / or wherein the processing beam (2)

is moved in a highly dynamic manner and at least two deflected machining beams (2 ', 2 ") each act on different spatial areas (220, 230) of the process zone (200).

7. The method according to claim 6, characterized in that each of the

Processing beams (2 ‘, 2 ″, 20, 22) act on another spatial area (220, 230) of the process zone (200).

8. The method according to any one of the preceding claims, characterized in that two acousto-optical deflectors rotated by 90 ° against each other are provided, by means of which a deflection of the processing beams (2 ‘, 2 ″, 20, 22) in one on the

Processing beam (2) perpendicular plane is carried out.

9. The method according to any one of the preceding claims, characterized in that the processing beam (2, 2 ', 2 ″, 20, 22) each sequentially and / or randomly and / or chaotically different spatial areas (220, 230) of the process zone (200 ) applied.

10. The method according to any one of the preceding claims, characterized in that the processing beams (2 ‘, 2 ″, 20, 22) are each shaped by means of a beam shaper (40) before they act on the different spatial areas (220, 230).

11. The method according to any one of the preceding claims, characterized in that the forming process zone (200) acted upon by the partial machining beams (20, 22) and the workpieces (1 10, 120) are moved relative to one another.

12. Device (1) for processing at least one workpiece (110, 120), wherein a

Beam source for providing a processing beam (2), preferably a pulsed laser beam, particularly preferably an ultrashort pulse laser beam, and an optical system (400) for impinging on at least one workpiece (110, 120) with the processing beam (2), the optical system (400) being provided. is designed and set up to move the processing beam (2) in a highly dynamic manner between at least two different spatial areas (220, 230) to form a process zone (200).

13. The device (1) according to claim 12, characterized in that at least two workpieces (110, 120) can be welded with it, at least one of the workpieces (110, 120) being transparent to the machining beam (2), the optical system ( 400) is designed and set up to split the machining beam (2) into at least two separate machining partial beams (20, 22) and with at least two

Processing partial beams (20, 22) each act on different spatial areas (220, 230) of the process zone (200).

14. Device (1) according to claim 12 or 13, characterized in that the optical

System (400) has an acousto-optic deflector (32) for the highly dynamic movement of the processing beam (2).

15. Device (1) according to claim 14, characterized in that the optical system (400) has two acousto-optical deflectors, by means of which a deflection of the processing partial beams (20, 22) is made possible in a plane perpendicular to the processing beam (2) .