EP3774675A1 - Method for the laser welding of transparent workpieces, and associated laser machining tool - Google Patents

Method for the laser welding of transparent workpieces, and associated laser machining tool

Info

Publication number
EP3774675A1
EP3774675A1 EP19717791.8A EP19717791A EP3774675A1 EP 3774675 A1 EP3774675 A1 EP 3774675A1 EP 19717791 A EP19717791 A EP 19717791A EP 3774675 A1 EP3774675 A1 EP 3774675A1
Authority
EP
European Patent Office
Prior art keywords
laser
laser beam
feed direction
workpieces
workpiece
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19717791.8A
Other languages
German (de)
French (fr)
Inventor
Malte Kumkar
Felix Zimmermann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Trumpf Laser und Systemtechnik GmbH
Original Assignee
Trumpf Laser und Systemtechnik GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Trumpf Laser und Systemtechnik GmbH filed Critical Trumpf Laser und Systemtechnik GmbH
Publication of EP3774675A1 publication Critical patent/EP3774675A1/en
Pending legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • B23K26/0624—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses using ultrashort pulses, i.e. pulses of 1ns or less
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/082—Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/083—Devices involving movement of the workpiece in at least one axial direction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/0869—Devices involving movement of the laser head in at least one axial direction
    • B23K26/0876—Devices involving movement of the laser head in at least one axial direction in at least two axial directions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/21—Bonding by welding
    • B23K26/24—Seam welding
    • B23K26/244—Overlap seam welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/20—Bonding
    • B23K26/32—Bonding taking account of the properties of the material involved
    • B23K26/324—Bonding taking account of the properties of the material involved involving non-metallic parts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50—Working by transmitting the laser beam through or within the workpiece
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50—Working by transmitting the laser beam through or within the workpiece
    • B23K26/57—Working by transmitting the laser beam through or within the workpiece the laser beam entering a face of the workpiece from which it is transmitted through the workpiece material to work on a different workpiece face, e.g. for effecting removal, fusion splicing, modifying or reforming
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B23/00—Re-forming shaped glass
    • C03B23/20—Uniting glass pieces by fusing without substantial reshaping
    • C03B23/203—Uniting glass sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B23K2103/52—Ceramics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B23K2103/54—Glass

Definitions

  • the invention relates to a method for laser welding of two overlapping workpieces by means of a pulsed laser beam, in particular UKP laser beam, which is directed through the one workpiece on the other workpiece and moved relative to the two workpieces in a feed direction to between the two abutting workpieces one To produce weld, as well as a suitable for carrying out this laser welding process laser processing machine.
  • a pulsed laser beam in particular UKP laser beam
  • Ultrashort pulsed (UKP) laser radiation with pulse durations less than 500 ps is increasingly used for material processing.
  • the peculiarity of material processing with UKP laser radiation lies in the short interaction time of the laser radiation with the workpiece. Due to this interaction time, extreme thermodynamic imbalances can be generated in the solid state, which then lead to unique ablation or formation mechanisms.
  • metals, semiconductors, dielectrics or composites can be removed with high precision with minimum heat input or formation processes of microstructures or nanostructures can be excited (eg Gottmann, J., Hermans, M., Ortmann, J., "Digital Photonic Production of Micro Structures in Glass by In-Volume Selective Laser-Induced Etching Using a High Speed Microscanner ", Physics Procedia 39, 2012, 534-541).
  • the laser welding of laser-transparent glasses or other materials transparent to the laser beam, partially transparent or scattering by means of ultrashort laser pulses enables a stable connection without additional material input, but is limited by laser-induced transient as well as permanent voltages.
  • a multiple crossing of the laser beam along the joint line of the joining partners, ie along the weld seam is therefore usually used.
  • the laser-induced voltage can also be reduced by means of suitable laser and / or process parameters, which, however, can result in other disadvantages (gap bridging capability).
  • the background is the local melting of the material by means of ultrashort laser pulses. Focusing ultrashort laser pulses into the volume of glass, e.g.
  • Quartz glass the high intensity in focus leads to non-linear absorption processes, whereby various material modifications can be induced, depending on the laser parameters. If the temporal pulse interval is shorter than the typical heat diffusion time of the glass, the temperature in the focus area increases from pulse to pulse (so-called heat accumulation). and can lead to local melting. If one places the modification in the area of the interface of two glasses, the cooling melt generates a stable connection of both glasses. Due to the local joining process, the laser-induced voltages are typically low, which can also thermally different glasses are bonded. However, these stresses affect the strength and can imitate the feasibility of laser bake I imi.
  • a line-shaped weld can specify a preferred plane along which cracks can propagate, which is therefore disadvantageous for the strength and can lead to material failure (breakage).
  • the present invention therefore has as its object to reduce in a method of the type mentioned in the laser-induced stresses in the workpieces to be welded together and a sufficiently stable
  • This object is achieved in accordance with the invention by superposing a deflection of the laser beam in the direction of movement of the laser beam moved in the feed direction.
  • the outward and outward deflection of the laser beam can take place transversely, in particular vertically, or parallel to the feed direction.
  • the deflection of the laser beam transversely to the feed direction comprises any deflection of the laser beam which does not run parallel to the feed direction.
  • the back and forth deflection of the laser beam perpendicular to the feed direction can also take place in the beam propagation direction.
  • the laser focus is advantageously not at the level of the joining surface, but in the volume of the lower or upper workpiece just below or above its joining surface. In this way, a melt volume can arise, which does not include the joining surfaces of the two workpieces.
  • the dynamic deflection of the laser beam transversely or parallel to the feed direction during the passage of the laser beam makes it possible to reduce or redistribute laser-induced stresses during the welding process, so that a higher strength is achieved in comparison to conventional welding.
  • the zigzag or serpentine weld seam produced by the dynamic deflection of the laser beam transversely to the feed direction produces on average lower stress or stress birefringence than in the case of a straight-line weld seam, with stress maxima occurring separately from one another.
  • Microscopic displacements (strains) due to the change in volume of the workpiece material can not accumulate along a preferred direction and thus predetermine no break line.
  • the required stability of the welded joint can be generated in a single pass.
  • the invention makes it possible to increase the strength of laser-bonded workpieces independently of whether the joining partners are subsequently treated for further quality improvement or not. Furthermore, the effective size of the molten surface can be increased, which in turn can improve the stability of the joint connection. Further advantages result from the fact that the melt volume increases and at the same time its geometry can be controlled more flexibly than before. The advantages of this melt, which is controlled in volume and geometry in a single pass, can be exploited both in terms of strength and throughput.
  • At least one workpiece is made of glass, in particular quartz glass, of polymer, glass ceramic, crystals or combinations thereof and / or with opaque materials and has a transparency of at least 90% at the laser wavelength.
  • This value refers to linear absorption processes of the laser beam in uncontaminated material.
  • the relative movement of the laser beam in the feed direction and transversely or parallel to the feed direction can be achieved solely by moving the workpieces, solely by deflecting the laser beam or by a combination thereof become.
  • the two workpieces are preferably moved exclusively in the feed direction and at the same time the laser beam is deflected exclusively transversely or parallel to the respective feed direction.
  • the feed speed and the deflection speed are advantageously selected such that the deflection speed is between 0.01 times and 100 times the feed rate.
  • the relative movement of the laser beam in the feed direction can take place along any arbitrary trajectory.
  • the two workpieces are moved at a constant feed rate in the feed direction and the laser beam is deflected periodically with the same amplitude across or parallel to the feed direction, in the former case a weld in the form of a regular zigzag line or a sine curve to create.
  • the welding process is based in particular on an absorption of the laser beam induced by nonlinear effects, which leads to the fact that the modification threshold of the respective material is exceeded, so that a permanent modification of the material occurs.
  • the parameters of all or part of the laser pulses are selected so that non-linear absorption processes occur and, as a result, the modification threshold is exceeded.
  • the welding process is initiated by one or more pulses whose parameters are selected such that processes occur which are induced by non-linear absorption and which lead to permanent material modifications.
  • the invention also relates to a laser processing machine for the laser welding of two overlapping workpieces, of which at least one, in particular also the other, has a transparency of at least 90% at the laser wavelength, with a laser, in particular a UKP Laser, for generating a pulsed laser beam, in particular in the form of UKP laser pulses, with a scanner for deflecting the laser beam transversely or parallel to a feed direction and with a machine controller programmed to control the scanner such that a Movement of the Laser beam is superimposed in the feed direction a directed transversely or parallel to the feed direction back and forth deflection of the laser beam.
  • a laser in particular a UKP Laser
  • a scanner for deflecting the laser beam transversely or parallel to a feed direction
  • a machine controller programmed to control the scanner such that a Movement of the Laser beam is superimposed in the feed direction a directed transversely or parallel to the feed direction back and forth deflection of the laser beam.
  • the movement of the laser beam in the feed direction can be effected by the scanner and / or by a movement unit for moving the two overlapping workpieces in a feed direction.
  • the scanner is formed by at least one electro-optical, acousto-optical, piezover foundeden or based on micro-electro-mechanical system technology deflector (scanner mirror).
  • FIG. 1 schematically shows a laser processing machine for laser welding two laser-transparent workpieces by means of a laser beam, wherein the upper workpiece is shown partially broken away;
  • FIGS. 2a, 2b show two different welds according to the invention on two laser-welded workpieces, wherein the upper workpiece is shown partially broken away;
  • FIG. 3 shows the polarization contrast intensity of a rectilinear and a zigzag weld on two laser-welded workpieces, each in a plan view of the lap joint of the two laser-welded workpieces.
  • the laser processing machine 1 shown in Fig. 1 is used for laser welding two overlapping workpieces 2a, 2b by means of a laser beam 3, wherein at least the top in Fig. 1 workpiece 2a, in particular also other, lower workpiece 2b, a transparency of at least 90% at the La laser wavelength and, for example, glass, in particular quartz glass, from
  • Polymer glass-ceramic, crystalline or combinations thereof and / or is formed with opa ken materials.
  • the laser processing machine 1 comprises a UKP laser 4 for generating the laser beam 3 in the form of UKP laser pulses 5 with pulse durations of less than 500 ps, in particular less than 10 ps, a movement unit (eg workpiece table) 6 movable in the XY direction to the common Moving the two workpieces 2a, 2b to be welded and a scanner 7 for two-dimensional deflection of the laser beam 3 on the two workpieces 2a, 2b to be welded.
  • a UKP laser 4 for generating the laser beam 3 in the form of UKP laser pulses 5 with pulse durations of less than 500 ps, in particular less than 10 ps
  • a movement unit (eg workpiece table) 6 movable in the XY direction to the common Moving the two workpieces 2a, 2b to be welded
  • a scanner 7 for two-dimensional deflection of the laser beam 3 on the two workpieces 2a, 2b to be welded.
  • the scanner 7 is, for example, a microscanner with a high-NA microscope objective.
  • the emitted by the UKP laser 4 UKP laser pulses 5 are deflected by a galvanometer scanner 7, the beam deflection is imaged via a telescope in the region of the focal plane of Mikroskopobjek- tivs.
  • the laser beam 3 can be deflected by the scanner 7 in two transverse axes, and the deflected laser beam 3 is imaged by means of a telescope (not shown) onto a microscope objective of the scanner 7 located just in front of the workpiece to be processed.
  • the beam deflection can also take place by means of electro-optical, acousto-optical, piezover plausibleer or on micro-electro-mechanical system engineering (MEMS) based deflectors.
  • MEMS micro-electro-mechanical system engineering
  • the laser beam 3 is directed onto the lower workpiece 2 b through the upper workpiece 2 a in FIG. 1 and, by moving the moving unit 6, relative to the two workpieces 2 a, 2 b along a straight line Feed path curve 8 moves to locally melt the two workpieces 2a, 2b at their abutting joining surfaces 9a, 9b and thus to connect with each other.
  • the laser beam 3 moved along the feed track curve 8 becomes a back and forth deflection directed at right angles to the respective feed direction 10 (double arrow 11). superimposed on the laser beam 3, to thereby produce on the upper side 8, for example, a zigzag or serpentine weld seam 12.
  • the laser focus of the focused laser beam 3 is advantageously not located on the joining surface but in the volume of the second workpiece 2b near its joining surface 9b.
  • the weld seam 12 can be formed by superposing a uniform feed motion and a periodic transverse deflection of the laser beam 3 as a regular zigzag line (FIG. 2 a) or as a sine curve (FIG. 2 b).
  • the zigzag or serpentine weld seam 12 causes, on average, lower stresses than a straight-line weld seam, wherein stress maxima occur separated from one another. Microscopic displacements (strains) due to the change in volume of the workpiece material can not accumulate along a preferred direction and thus predetermine no break line.
  • the laser-induced voltages during the passage of the laser beam 3 are reduced or redistributed, so that a higher strength is achieved in comparison with the conventional laser welding.
  • the laser beam 3 moved along the feed path curve 8 can also be overlaid with a reciprocating deflection of the laser beam 3 directed parallel to the respective feed direction 10, thereby producing a longitudinal weld seam (not shown) on the upper side 8.
  • the following laser parameters are selected:
  • the modification threshold at a pulse duration of about 1 ps and a laser wavelength of about 1 pm is, for example, in the case of glass in volume at about 1 to 5 J / cm 2 , at the surface at about 0.1 -0 , 5 J / cm 2 .
  • a measure of the laser-induced stresses is the polarization contrast intensity, which in FIG straight line weld (curve a) and the inventive zigzag or serpentine weld (curve b) is shown.
  • the induced stress in the rectilinear weld (a) is comparably high over the entire modified range and indicates a uniform, continuous stress distribution.
  • Weld seam (b) shows, on average, lower maximum stresses with intensity peaks occurring separated from one another, as a result of which the strength of the laser-bonded connection is increased.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Laser Beam Processing (AREA)

Abstract

In a method for laser welding two overlapping workpieces (2a, 2b) by means of a pulsed laser beam (3), more particularly an ultrashort pulse laser beam, which is directed through one workpiece (2a) to the other workpiece (2b) and is moved in a feed direction (10) relative to the two workpieces (2a, 2b) in order to create a weld seam (12) between the two workpieces (2a, 2b) resting against each other, the invention proposes that a deflection (11) back and forth of the laser beam (3) directed transverse or parallel to the feed direction (10) is superimposed on the laser beam (3) moved in the feed direction (10).

Description

Verfahren zum Laserschweißen von transparenten Werkstücken  Method for laser welding transparent workpieces
und zugehörige Laserbearbeitunqsmaschine  and associated laser processing machine
Die Erfindung betrifft ein Verfahren zum Laserschweißen zweier einander überlap- pender Werkstücke mittels eines gepulsten Laserstrahls, insbesondere UKP- Laserstrahls, der durch das eine Werkstück hindurch auf das andere Werkstück gerichtet und relativ zu den beiden Werkstücken in einer Vorschubrichtung bewegt wird, um zwischen den beiden aneinander anliegenden Werkstücken eine Schweißnaht zu erzeugen, sowie auch eine zum Durchführen dieses Laser- schweißverfahrens geeignete Laserbearbeitungsmaschine. The invention relates to a method for laser welding of two overlapping workpieces by means of a pulsed laser beam, in particular UKP laser beam, which is directed through the one workpiece on the other workpiece and moved relative to the two workpieces in a feed direction to between the two abutting workpieces one To produce weld, as well as a suitable for carrying out this laser welding process laser processing machine.
Ultrakurz gepulste (UKP)-Laserstrahlung mit Pulsdauern kleiner als 500 ps wird zunehmend für die Materialbearbeitung eingesetzt. Die Besonderheit der Material- bearbeitung mit UKP-Laserstrahlung liegt in der kurzen Wechselwirkungszeit der Laserstrahlung mit dem Werkstück. Bedingt durch diese Wechselwirkungszeit las- sen sich im Festkörper extreme thermodynamische Ungleichgewichte erzeugen, die dann zu einzigartigen Abtrags- oder Formationsmechanismen führen. So kön- nen beispielsweise Metalle, Halbleiter, Dielektrika oder Verbundstoffe unter mini- malem Wärmeeintrag hochpräzise abgetragen oder Formationsprozesse von Mikro- bzw. Nanostrukturen angeregt werden (z.B. Gottmann, J., Hermans, M., Ortmann, J.,“Digital Photonic Production of Micro Structures in Glass by In-Vo- lume Selective Laser-Induced Etching using a High Speed Micro Scanner”, Phy- sics Procedia 39, 2012, 534-541 ). Ultrashort pulsed (UKP) laser radiation with pulse durations less than 500 ps is increasingly used for material processing. The peculiarity of material processing with UKP laser radiation lies in the short interaction time of the laser radiation with the workpiece. Due to this interaction time, extreme thermodynamic imbalances can be generated in the solid state, which then lead to unique ablation or formation mechanisms. Thus, for example, metals, semiconductors, dielectrics or composites can be removed with high precision with minimum heat input or formation processes of microstructures or nanostructures can be excited (eg Gottmann, J., Hermans, M., Ortmann, J., "Digital Photonic Production of Micro Structures in Glass by In-Volume Selective Laser-Induced Etching Using a High Speed Microscanner ", Physics Procedia 39, 2012, 534-541).
Das Laserschweißen von lasertransparenten Gläsern oder auch anderen, für den Laserstrahl transparenten, teiltransparenten oder streuenden Materialien mittels ultrakurzer Laserpulse ermöglicht eine stabile Verbindung ohne zusätzlichen Ma- terialeinsatz, ist aber durch laserinduzierte transiente sowie permanente Spannun- gen limitiert. Zur Steigerung des Anbindungsquerschnittes wird daher meist eine Mehrfachüberfahrt des Laserstrahls entlang der Fügelinie der Fügepartner, also entlang der Schweißnaht, genutzt. Prinzipiell kann die laserinduzierte Spannung auch mittels geeigneter Laser- und/oder Prozessparameter reduziert werden, wodurch sich allerdings andere Nachteile (Spaltüberbrückbarkeit) ergeben kön- nen. The laser welding of laser-transparent glasses or other materials transparent to the laser beam, partially transparent or scattering by means of ultrashort laser pulses enables a stable connection without additional material input, but is limited by laser-induced transient as well as permanent voltages. To increase the connection cross-section, a multiple crossing of the laser beam along the joint line of the joining partners, ie along the weld seam, is therefore usually used. In principle, the laser-induced voltage can also be reduced by means of suitable laser and / or process parameters, which, however, can result in other disadvantages (gap bridging capability).
Hintergrund ist das lokale Aufschmelzen des Materials mittels ultrakurzer Laser- pulse. Fokussiert man ultrakurze Laserpulse in das Volumen von Glas, z.B. The background is the local melting of the material by means of ultrashort laser pulses. Focusing ultrashort laser pulses into the volume of glass, e.g.
Quarzglas, führt die im Fokus vorliegende hohe Intensität zu nichtlinearen Ab- sorptionsprozessen, wodurch, in Abhängigkeit der Laserparameter, verschie- dene Materialmodifikationen induziert werden können. Wenn der zeitliche Puls- abstand kürzer als die typische Wärmediffusionszeit des Glases ist, erhöht sich die Temperatur im Fokusbereich von Puls zu Puls (sog. Wärmeakkumulation) und kann zum lokalen Aufschmelzen führen. Platziert man die Modifikation im Bereich der Grenzfläche zweier Gläser, generiert die abkühlende Schmelze eine stabile Verbindung beider Gläser. Aufgrund des lokalen Fügeprozesses sind die laserinduzierten Spannungen typischerweise gering, wodurch auch thermisch stark verschiedene Gläser gebondet werden können. Jedoch beeinflussen diese Spannungen die Festigkeit und können die Machbarkeit des Laserbondens I imi tieren . Neben der Größe der Modifikation, die von Prozessparametern, wie z.B. der mittleren Laserleistung sowie dem Pulsüberlapp, abhängt, hat auch die Geo- metrie der Schweißnaht einen entscheidenden Einfluss auf die laserinduzierten Spannungen. So kann eine linienförmige Schweißnaht eine bevorzugte Ebene vorgeben, entlang der Risse propagieren können, was somit für die Festigkeit von Nachteil ist und zu Materialversagen (Bruch) führen kann. Quartz glass, the high intensity in focus leads to non-linear absorption processes, whereby various material modifications can be induced, depending on the laser parameters. If the temporal pulse interval is shorter than the typical heat diffusion time of the glass, the temperature in the focus area increases from pulse to pulse (so-called heat accumulation). and can lead to local melting. If one places the modification in the area of the interface of two glasses, the cooling melt generates a stable connection of both glasses. Due to the local joining process, the laser-induced voltages are typically low, which can also thermally different glasses are bonded. However, these stresses affect the strength and can imitate the feasibility of laser bake I imi. In addition to the size of the modification, which depends on process parameters, such as the mean laser power and the pulse overlap, the geometry of the weld also has a decisive influence on the laser-induced stresses. Thus, a line-shaped weld can specify a preferred plane along which cracks can propagate, which is therefore disadvantageous for the strength and can lead to material failure (breakage).
Die vorliegende Erfindung stellt sich daher die Aufgabe, bei einem Verfahren der eingangs genannten Art die in den miteinander zu verschweißenden Werkstücken laserinduzierten Spannungen zu reduzieren und eine ausreichend stabile The present invention therefore has as its object to reduce in a method of the type mentioned in the laser-induced stresses in the workpieces to be welded together and a sufficiently stable
Schweißnaht möglichst in einer einzigen Überfahrt zu erzeugen, sowie auch eine geeignete Laserbearbeitungsmaschine anzugeben. To produce weld as possible in a single crossing, as well as specify a suitable laser processing machine.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, dass dem in der Vorschub- richtung bewegten Laserstrahl eine Hin- und Herauslenkung des Laserstrahls überlagert wird. Die Hin- und Herauslenkung des Laserstrahls kann quer, insbe- sondere senkrecht, oder parallel zur Vorschubrichtung erfolgen. Die Hin- und Her- auslenkung des Laserstrahls quer zur Vorschubrichtung umfasst dabei jede Ablen- kung des Laserstrahls, die nicht parallel zur Vorschubrichtung verläuft. Die Hin- und Herauslenkung des Laserstrahls senkrecht zur Vorschubrichtung kann insbe- sondere auch in Strahlausbreitungsrichtung erfolgen. Durch eine Hin-und Heraus- lenkung des Laserstrahls quer zur Vorschubrichtung kann eine zickzack- oder schlangenlinienförmige Schweißnaht erzeugt werden. Der Laserfokus befindet sich dabei vorteilhaft nicht auf Höhe der Fügefläche, sondern im Volumen des un- teren oder oberen Werkstücks knapp unter- bzw. oberhalb seiner Fügefläche. Auf diese Weise kann ein Schmelzvolumen entstehen, welche nicht die Fügeflächen der beiden Werkstücke einschließt. Erfindungsgemäß ermöglichst es die dynamische Ablenkung des Laserstrahls quer oder parallel zur Vorschubrichtung während der Überfahrt des Laserstrahls, die während des Schweißprozesses laserinduzierten Spannungen zu reduzieren bzw. umzuverteilen, sodass eine höhere Festigkeit im Vergleich zum herkömmli- chen Schweißen erreicht wird. Insbesondere bewirkt die durch die dynamische Ablenkung des Laserstrahls quer zur Vorschubrichtung erzeugte zickzack- oder schlangenlinienförmige Schweißnaht eine im Mittel geringere Spannung bzw. Spannungsdoppelbrechung als bei einer geradlinigen Schweißnaht, wobei Span- nungsmaxima voneinander separiert auftreten. Mikroskopische Verschiebungen (Dehnungen) aufgrund der Volumenänderung des Werkstückmaterials können sich nicht entlang einer Vorzugsrichtung aufsummieren und somit keine Bruchlinie vorgeben. Insbesondere bei nicht-gradlinigen Schweißnähten kann die erforderli- che Stabilität der Schweißverbindung in einer einzigen Überfahrt erzeugt werden. This object is achieved in accordance with the invention by superposing a deflection of the laser beam in the direction of movement of the laser beam moved in the feed direction. The outward and outward deflection of the laser beam can take place transversely, in particular vertically, or parallel to the feed direction. In this case, the deflection of the laser beam transversely to the feed direction comprises any deflection of the laser beam which does not run parallel to the feed direction. The back and forth deflection of the laser beam perpendicular to the feed direction can also take place in the beam propagation direction. By a forward and outward deflection of the laser beam transversely to the feed direction, a zigzag or serpentine weld can be produced. The laser focus is advantageously not at the level of the joining surface, but in the volume of the lower or upper workpiece just below or above its joining surface. In this way, a melt volume can arise, which does not include the joining surfaces of the two workpieces. According to the invention, the dynamic deflection of the laser beam transversely or parallel to the feed direction during the passage of the laser beam makes it possible to reduce or redistribute laser-induced stresses during the welding process, so that a higher strength is achieved in comparison to conventional welding. In particular, the zigzag or serpentine weld seam produced by the dynamic deflection of the laser beam transversely to the feed direction produces on average lower stress or stress birefringence than in the case of a straight-line weld seam, with stress maxima occurring separately from one another. Microscopic displacements (strains) due to the change in volume of the workpiece material can not accumulate along a preferred direction and thus predetermine no break line. Particularly in the case of non-rectilinear welds, the required stability of the welded joint can be generated in a single pass.
Die Erfindung ermöglicht es, die Festigkeit laser-gebondeter Werkstücke unabhän- gig davon zu erhöhen, ob die Fügepartner nachträglich noch zur weiteren Quali- tätsverbesserung behandelt werden oder nicht. Des Weiteren kann die effektive Größe der aufgeschmolzenen Fläche vergrößert werden, die wiederum die Stabili tät der Fügeverbindung verbessern kann. Weitere Vorteile ergeben sich dadurch, dass das Schmelzvolumen vergrößert und gleichzeitig dessen Geometrie flexibler als bisher kontrolliert werden kann. Dabei lassen sich die Vorteile dieser in einer einzigen Überfahrt in Volumen und Geometrie kontrollierten Schmelze sowohl im Hinblick auf die Festigkeit als auch den Durchsatz nutzen. The invention makes it possible to increase the strength of laser-bonded workpieces independently of whether the joining partners are subsequently treated for further quality improvement or not. Furthermore, the effective size of the molten surface can be increased, which in turn can improve the stability of the joint connection. Further advantages result from the fact that the melt volume increases and at the same time its geometry can be controlled more flexibly than before. The advantages of this melt, which is controlled in volume and geometry in a single pass, can be exploited both in terms of strength and throughput.
Vorzugsweise ist zumindest das eine Werkstück, insbesondere auch das andere Werkstück, aus Glas, insbesondere Quarzglas, aus Polymer, Glaskeramik, Kristal- len oder Kombinationen davon und/oder mit opaken Materialien gebildet und weist eine Transparenz von mindestens 90% bei der Laserwellenlänge auf. Dabei be- zieht sich dieser Wert auf lineare Absorptionsprozesse des Laserstrahls in unbe- handeltem Material. Preferably, at least one workpiece, in particular also the other workpiece, is made of glass, in particular quartz glass, of polymer, glass ceramic, crystals or combinations thereof and / or with opaque materials and has a transparency of at least 90% at the laser wavelength. This value refers to linear absorption processes of the laser beam in uncontaminated material.
Prinzipiell kann die Relativbewegung des Laserstrahls in Vorschubrichtung und quer bzw. parallel zur Vorschubrichtung allein durch Bewegen der Werkstücke, al- lein durch Ablenken des Laserstrahls oder durch eine Kombination davon erreicht werden. Im letzteren Fall werden bevorzugt die beiden Werkstücke ausschließlich in Vorschubrichtung bewegt und gleichzeitig der Laserstrahl ausschließlich quer oder parallel zur jeweiligen Vorschubrichtung abgelenkt. Die Vorschubgeschwin- digkeit und die Ablenkgeschwindigkeit werden vorteilhaft so gewählt, dass die Ab- lenkgeschwindigkeit zwischen dem 0,01 -fachen und dem 100-fachen der Vor- schubgeschwindigkeit beträgt. Grundsätzlich kann die Relativbewegung des La- serstrahls in Vorschubrichtung entlang jeder beliebigen Bahnkurve erfolgen. In principle, the relative movement of the laser beam in the feed direction and transversely or parallel to the feed direction can be achieved solely by moving the workpieces, solely by deflecting the laser beam or by a combination thereof become. In the latter case, the two workpieces are preferably moved exclusively in the feed direction and at the same time the laser beam is deflected exclusively transversely or parallel to the respective feed direction. The feed speed and the deflection speed are advantageously selected such that the deflection speed is between 0.01 times and 100 times the feed rate. In principle, the relative movement of the laser beam in the feed direction can take place along any arbitrary trajectory.
In einer Verfahrensvariante werden die beiden Werkstücke mit konstanter Vor- schubgeschwindigkeit in der Vorschubrichtung bewegt und der Laserstrahl perio- disch mit gleicher Amplitude quer oder parallel zur Vorschubrichtung hin- und her abgelenkt, um im ersteren Fall eine Schweißnaht in Form einer regelmäßigen Zickzacklinie oder einer Sinuskurve zu erzeugen. In a variant of the method, the two workpieces are moved at a constant feed rate in the feed direction and the laser beam is deflected periodically with the same amplitude across or parallel to the feed direction, in the former case a weld in the form of a regular zigzag line or a sine curve to create.
Der Schweißprozess basiert dabei insbesondere auf einer durch nichtlineare Ef- fekte induzierten Absorption des Laserstrahls, welche dazu führt, dass die Modifi- kationsschwelle des jeweiligen Materials überschritten wird, so dass es zu einer permanenten Modifikation des Materials kommt. Dabei werden die Parameter aller oder eines Teils der Laserpulse so gewählt, dass nichtlineare Absorptionspro- zesse auftreten und daraus resultierend die Modifikationsschwelle überschritten wird. Insbesondere wird der Schweißprozess durch einen oder mehrere Pulse initi- iert, dessen bzw. deren Parameter so gewählt sind, dass Prozesse auftreten, wel- che durch nichtlineare Absorption induziert werden und welche zu permanenten Materialmodifikationen führen. The welding process is based in particular on an absorption of the laser beam induced by nonlinear effects, which leads to the fact that the modification threshold of the respective material is exceeded, so that a permanent modification of the material occurs. The parameters of all or part of the laser pulses are selected so that non-linear absorption processes occur and, as a result, the modification threshold is exceeded. In particular, the welding process is initiated by one or more pulses whose parameters are selected such that processes occur which are induced by non-linear absorption and which lead to permanent material modifications.
Die Erfindung betrifft in einem weiteren Aspekt auch eine Laserbearbeitungsma- schine zum Laserschweißen zweier einander überlappender Werkstücke, von de- nen zumindest eines, insbesondere auch das andere, eine Transparenz von min- destens 90% bei der Laserwellenlänge aufweist, mit einem Laser, insbesondere UKP-Laser, zum Erzeugen eines gepulsten Laserstrahls, insbesondere in Form von UKP-Laserpulsen, mit einem Scanner zum Ablenken des Laserstrahls quer o- der parallel zu einer Vorschubrichtung und mit einer Maschinensteuerung, die pro- grammiert ist, den Scanner derart anzusteuern, dass einer Bewegung des Laserstrahls in der Vorschubrichtung eine quer oder parallel zur Vorschubrichtung gerichtete Hin- und Herablenkung des Laserstrahls überlagert wird. In a further aspect, the invention also relates to a laser processing machine for the laser welding of two overlapping workpieces, of which at least one, in particular also the other, has a transparency of at least 90% at the laser wavelength, with a laser, in particular a UKP Laser, for generating a pulsed laser beam, in particular in the form of UKP laser pulses, with a scanner for deflecting the laser beam transversely or parallel to a feed direction and with a machine controller programmed to control the scanner such that a Movement of the Laser beam is superimposed in the feed direction a directed transversely or parallel to the feed direction back and forth deflection of the laser beam.
Die Bewegung des Laserstrahls in Vorschubrichtung kann durch den Scanner und/oder durch eine Bewegungseinheit zum Bewegen der beiden einander über- lappenden Werkstücke in einer Vorschubrichtung erfolgen. The movement of the laser beam in the feed direction can be effected by the scanner and / or by a movement unit for moving the two overlapping workpieces in a feed direction.
Vorzugsweise ist der Scanner durch mindestens einen elektro-optischen, akusto- optischen, piezoverstellbaren oder auf mikro-elektromechanischer Systemtechnik basierenden Deflektor (Scannerspiegel) gebildet. Preferably, the scanner is formed by at least one electro-optical, acousto-optical, piezoverstellbaren or based on micro-electro-mechanical system technology deflector (scanner mirror).
Weitere Vorteile und vorteilhafte Ausgestaltungen des Gegenstands der Erfindung ergeben sich aus der Beschreibung, den Ansprüchen und der Zeichnung. Ebenso können die vorstehend genannten und die noch weiter aufgeführten Merkmale je für sich oder zu mehreren in beliebigen Kombinationen Verwendung finden. Die gezeigten und beschriebenen Ausführungsformen sind nicht als abschließende Aufzählung zu verstehen, sondern haben vielmehr beispielhaften Charakter für die Schilderung der Erfindung. Es zeigen: Further advantages and advantageous embodiments of the subject invention will become apparent from the description, the claims and the drawings. Likewise, the features mentioned above and the features listed further can be used individually or in combination in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention. Show it:
Fig. 1 schematisch eine Laserbearbeitungsmaschine zum Laserschweißen zweier lasertransparenter Werkstücke mittels eines Laserstrahls, wo- bei das obere Werkstück teilweise aufgebrochen dargestellt ist; 1 schematically shows a laser processing machine for laser welding two laser-transparent workpieces by means of a laser beam, wherein the upper workpiece is shown partially broken away;
Fign. 2a, 2b zwei verschiedene erfindungsgemäße Schweißnähte an zwei laser- geschweißten Werkstücken, wobei das obere Werkstück teilweise aufgebrochen dargestellt ist; und  FIGS. 2a, 2b show two different welds according to the invention on two laser-welded workpieces, wherein the upper workpiece is shown partially broken away; and
Fig. 3 die Polarisationskontrastintensität einer geradlinigen und einer zick- zackförmigen Schweißnaht an zwei lasergeschweißten Werkstücken, jeweils in einer Draufsicht auf den Überlappstoß der beiden laserge- schweißten Werkstücke.  3 shows the polarization contrast intensity of a rectilinear and a zigzag weld on two laser-welded workpieces, each in a plan view of the lap joint of the two laser-welded workpieces.
Die in Fig. 1 gezeigte Laserbearbeitungsmaschine 1 dient zum Laserschweißen zweier einander überlappender Werkstücke 2a, 2b mittels eines Laserstrahls 3, wobei zumindest das in Fig. 1 obere Werkstück 2a, insbesondere auch das andere, untere Werkstück 2b, eine Transparenz von mindestens 90% bei der La- serwellenlänge aufweist und beispielsweise aus Glas, insbesondere Quarzglas, aus The laser processing machine 1 shown in Fig. 1 is used for laser welding two overlapping workpieces 2a, 2b by means of a laser beam 3, wherein at least the top in Fig. 1 workpiece 2a, in particular also other, lower workpiece 2b, a transparency of at least 90% at the La laser wavelength and, for example, glass, in particular quartz glass, from
Polymer, Glaskeramik, kristallin oder aus Kombinationen davon und/oder mit opa- ken Materialien gebildet ist.  Polymer, glass-ceramic, crystalline or combinations thereof and / or is formed with opa ken materials.
Die Laserbearbeitungsmaschine 1 umfasst einen UKP-Laser 4 zum Erzeugen des Laserstrahls 3 in Form von UKP-Laserpulsen 5 mit Pulsdauern kleiner als 500 ps, insbesondere kleiner als 10 ps, eine in X-Y-Richtung bewegbare Bewegungsein- heit (z.B. Werkstücktisch) 6 zum gemeinsamen Bewegen der beiden zu ver- schweißenden Werkstücke 2a, 2b, sowie einen Scanner 7 zum zweidimensionalen Ablenken des Laserstrahls 3 auf den beiden zu verschweißenden Werkstücken 2a, 2b. The laser processing machine 1 comprises a UKP laser 4 for generating the laser beam 3 in the form of UKP laser pulses 5 with pulse durations of less than 500 ps, in particular less than 10 ps, a movement unit (eg workpiece table) 6 movable in the XY direction to the common Moving the two workpieces 2a, 2b to be welded and a scanner 7 for two-dimensional deflection of the laser beam 3 on the two workpieces 2a, 2b to be welded.
Bei dem Scanner 7 handelt es sich beispielsweise um einen Microscanner mit Hoch-NA-Mikroskopobjektiv. Hierbei werden die vom UKP-Laser 4 emittierten UKP-Laserpulse 5 durch einen Galvanometerscanner 7 abgelenkt, dessen Strahl ablenkung über ein Teleskop in den Bereich der Brennebene des Mikroskopobjek- tivs abgebildet wird. Der Laserstrahl 3 kann vom Scanner 7 in zwei transversalen Achsen abgelenkt werden, und der abgelenkte Laserstrahl 3 wird mittels eines nicht gezeigten Teleskops auf ein kurz vor dem zu bearbeitenden Werkstück be- findliches Mikroskopobjektiv des Scanners 7 abgebildet. Alternativ kann die Strahl- ablenkung auch mittels elektro-optischer, akusto-optischer, piezoverstellbarer oder auch auf mikro-elektromechanischer Systemtechnik (MEMS) basierender Deflek- toren erfolgen. The scanner 7 is, for example, a microscanner with a high-NA microscope objective. In this case, the emitted by the UKP laser 4 UKP laser pulses 5 are deflected by a galvanometer scanner 7, the beam deflection is imaged via a telescope in the region of the focal plane of Mikroskopobjek- tivs. The laser beam 3 can be deflected by the scanner 7 in two transverse axes, and the deflected laser beam 3 is imaged by means of a telescope (not shown) onto a microscope objective of the scanner 7 located just in front of the workpiece to be processed. Alternatively, the beam deflection can also take place by means of electro-optical, acousto-optical, piezoverstellbarer or on micro-electro-mechanical system engineering (MEMS) based deflectors.
Beim Laserschweißen der beiden Werkstücke 2a, 2b wird der Laserstrahl 3 durch das in Fig. 1 obere Werkstück 2a hindurch auf das untere Werkstück 2b gerichtet und - durch Bewegen der Bewegungseinheit 6 - relativ zu den beiden Werkstü- cken 2a, 2b entlang einer hier gradlinigen Vorschubbahnkurve 8 bewegt, um die beiden Werkstücke 2a, 2b an ihren aneinander anliegenden Fügeflächen 9a, 9b lokal aufzuschmelzen und somit miteinander zu verbinden. Dem entlang der Vor- schubbahnkurve 8 bewegten Laserstrahl 3 wird eine quer, hier rechtwinklig, zur je- weiligen Vorschubrichtung 10 gerichtete Hin- und Herablenkung (Doppelpfeil 11) des Laserstrahls 3 überlagert, um dadurch auf der Oberseite 8 eine bspw. zick- zack- oder schlangenlinienförmige Schweißnaht 12 zu erzeugen. Der Laserfokus des fokussierten Laserstrahls 3 befindet sich dabei vorteilhaft nicht auf der Füge- fläche, sondern im Volumen des zweiten Werkstücks 2b nahe seiner Fügefläche 9b. Die Schweißnaht 12 kann durch Überlagerung einer gleichförmigen Vorschub- bewegung und einer periodischen Querablenkung des Laserstrahls 3 als regelmä- ßige Zickzacklinie (Fig. 2a) oder als Sinuskurve (Fig. 2b) ausgebildet sein. In the case of laser welding of the two workpieces 2 a, 2 b, the laser beam 3 is directed onto the lower workpiece 2 b through the upper workpiece 2 a in FIG. 1 and, by moving the moving unit 6, relative to the two workpieces 2 a, 2 b along a straight line Feed path curve 8 moves to locally melt the two workpieces 2a, 2b at their abutting joining surfaces 9a, 9b and thus to connect with each other. The laser beam 3 moved along the feed track curve 8 becomes a back and forth deflection directed at right angles to the respective feed direction 10 (double arrow 11). superimposed on the laser beam 3, to thereby produce on the upper side 8, for example, a zigzag or serpentine weld seam 12. The laser focus of the focused laser beam 3 is advantageously not located on the joining surface but in the volume of the second workpiece 2b near its joining surface 9b. The weld seam 12 can be formed by superposing a uniform feed motion and a periodic transverse deflection of the laser beam 3 as a regular zigzag line (FIG. 2 a) or as a sine curve (FIG. 2 b).
Die zickzack- oder schlangenlinienförmige Schweißnaht 12 bewirkt im Mittel gerin- gere Spannungen als eine geradlinige Schweißnaht, wobei Spannungsmaxima voneinander separiert auftreten. Mikroskopische Verschiebungen (Dehnungen) aufgrund der Volumenänderung des Werkstückmaterials können sich nicht entlang einer Vorzugsrichtung aufsummieren und somit keine Bruchlinie vorgeben. Die während der Überfahrt des Laserstrahls 3 laserinduzierten Spannungen werden reduziert bzw. umverteilt, sodass eine höhere Festigkeit im Vergleich zum her- kömmlichen Laserschweißen erreicht wird. The zigzag or serpentine weld seam 12 causes, on average, lower stresses than a straight-line weld seam, wherein stress maxima occur separated from one another. Microscopic displacements (strains) due to the change in volume of the workpiece material can not accumulate along a preferred direction and thus predetermine no break line. The laser-induced voltages during the passage of the laser beam 3 are reduced or redistributed, so that a higher strength is achieved in comparison with the conventional laser welding.
Statt wie gezeigt quer, kann dem entlang der Vorschubbahnkurve 8 bewegten La- serstrahl 3 auch eine parallel zur jeweiligen Vorschubrichtung 10 gerichtete Hin- und Herablenkung des Laserstrahls 3 überlagert werden, um dadurch auf der Oberseite 8 eine longitudinale Schweißnaht (nicht gezeigt) zu erzeugen. Instead of transversely as shown, the laser beam 3 moved along the feed path curve 8 can also be overlaid with a reciprocating deflection of the laser beam 3 directed parallel to the respective feed direction 10, thereby producing a longitudinal weld seam (not shown) on the upper side 8.
Vorzugsweise werden folgende Laserparameter gewählt: Preferably, the following laser parameters are selected:
Laserwellenlänge zwischen 200 und 5000 nm,  Laser wavelength between 200 and 5000 nm,
Repetitionsrate der Laserpulse zwischen 1 kHz und 500 GHz,  Repetition rate of the laser pulses between 1 kHz and 500 GHz,
Laserpulsdauer zwischen 10 fs und 500 ps,  Laser pulse duration between 10 fs and 500 ps,
Fokussierung und Pulsenergie so, dass die Fluenz in der Fokuszone größer als 0.01 J/cm2 ist. Focusing and pulse energy so that the fluence in the focus zone is greater than 0.01 J / cm 2 .
Die Modifikationsschwelle bei einer Pulsdauer von ca. 1 ps und einer Laserwellen- länge von ca. 1 pm liegt dabei bspw. bei Glas im Volumen bei ca. 1 bis 5 J/cm2 , an der Oberfläche bei ca. 0,1 -0,5 J/cm2. The modification threshold at a pulse duration of about 1 ps and a laser wavelength of about 1 pm is, for example, in the case of glass in volume at about 1 to 5 J / cm 2 , at the surface at about 0.1 -0 , 5 J / cm 2 .
Ein Maß für die laserinduzierten Spannungen (Spannungsdoppelbrechung) ist die Polarisationskontrastintensität, die in Fig. 3 exemplarisch für den Fall einer geradlinigen Schweißnaht (Kurve a) und der erfindungsgemäßen zickzack- oder schlangenlinienförmigen Schweißnaht (Kurve b) dargestellt ist. Die induzierte Spannung ist bei der geradlinigen Schweißnaht (a) über den gesamten modifizier- ten Bereich vergleichbar hoch und deutet auf eine einheitliche, zusammenhän- gende Spannungsverteilung hin. Die zickzack- oder schlangenlinienförmigeA measure of the laser-induced stresses (stress birefringence) is the polarization contrast intensity, which in FIG straight line weld (curve a) and the inventive zigzag or serpentine weld (curve b) is shown. The induced stress in the rectilinear weld (a) is comparably high over the entire modified range and indicates a uniform, continuous stress distribution. The zigzag or serpentine
Schweißnaht (b) zeigt im Mittel geringere Spannungsmaxima mit voneinander se- pariert auftretenden Intensitätsspitzen, wodurch die Festigkeit der lasergebonde- ten Verbindung erhöht ist. Weld seam (b) shows, on average, lower maximum stresses with intensity peaks occurring separated from one another, as a result of which the strength of the laser-bonded connection is increased.

Claims

Patentansprüche claims
1. Verfahren zum Laserschweißen zweier einander überlappender Werkstü- cke (2a, 2b) mittels eines gepulsten Laserstrahls (3), insbesondere UKP- Laserstrahls, der durch das eine Werkstück (2a) hindurch auf das andere Werkstück (2b) gerichtet und relativ zu den beiden Werkstücken (2a, 2b) in einer Vorschubrichtung (10) bewegt wird, um zwischen den beiden an- einander anliegenden Werkstücken (2a, 2b) eine Schweißnaht (12) zu er- zeugen, 1. A method for laser welding two overlapping workpieces (2a, 2b) by means of a pulsed laser beam (3), in particular UKP laser beam which through the one workpiece (2a) directed to the other workpiece (2b) and relative to the two workpieces (2a, 2b) is moved in a feed direction (10) in order to produce a weld seam (12) between the two adjacent workpieces (2a, 2b),
dadurch gekennzeichnet,  characterized,
dass dem in der Vorschubrichtung (10) bewegten Laserstrahl (3) eine quer oder parallel zur Vorschubrichtung (10) gerichtete Hin- und Herablenkung (11 ) des Laserstrahls (3) überlagert wird.  in that a reciprocating deflection (11) of the laser beam (3) directed transversely or parallel to the feed direction (10) is superimposed on the laser beam (3) moved in the feed direction (10).
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass zumindest das eine Werkstück (2a), insbesondere auch das andere Werkstück (2b), aus Glas, insbesondere Quarzglas, aus Polymer, Glaskeramik, kristallin oder aus Kombinationen davon und/oder mit opaken Materialien gebildet ist. 2. The method according to claim 1, characterized in that at least one workpiece (2a), in particular the other workpiece (2b), made of glass, in particular quartz glass, of polymer, glass ceramic, crystalline or combinations thereof and / or with opaque materials is formed.
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass das eine Werkstück (2a), insbesondere auch das andere Werkstück (2b), eine Transparenz von mindestens 90% bei der Laserwellenlänge aufweist. 3. The method according to claim 1 or 2, characterized in that the one workpiece (2a), in particular also the other workpiece (2b), has a transparency of at least 90% at the laser wavelength.
4. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekenn- zeichnet, dass die beiden Werkstücke (2a, 2b) ausschließlich in der Vor- schubrichtung (10) bewegt werden und gleichzeitig der Laserstrahl (3) ausschließlich quer oder parallel zur Vorschubrichtung (10) hin und her abgelenkt wird. 4. The method according to any one of the preceding claims, characterized in that the two workpieces (2a, 2b) are moved exclusively in the feed direction (10) and at the same time the laser beam (3) exclusively transverse or parallel to the feed direction (10). is distracted back and forth.
5. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekenn- zeichnet, dass die beiden Werkstücke (2a, 2b) mit konstanter Vorschubge- schwindigkeit (v) oder beschleunigt in der Vorschubrichtung (10) bewegt werden. 5. The method according to any one of the preceding claims, characterized in that the two workpieces (2a, 2b) at a constant feed rate (v) or accelerated in the feed direction (10) are moved.
6. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekenn- zeichnet, dass der Laserstrahl (3) periodisch mit gleicher Amplitude quer zur Vorschubrichtung (10) hin- und her abgelenkt wird, um eine Schweiß- naht (12) insbesondere in Form einer regelmäßigen Zickzacklinie oder ei- ner Sinuskurve zu erzeugen. 6. The method according to any one of the preceding claims, characterized in that the laser beam (3) is deflected back and forth periodically with the same amplitude transversely to the feed direction (10) to a weld seam (12), in particular in the form of a regular To create a zigzag line or a sinusoid.
7. Verfahren nach einem der vorhergehenden Ansprüche, dadurch gekenn- zeichnet, dass ein oder mehrere Pulse des gepulsten Laserstrahls (3) Pa- rameter aufweisen, welche so gewählt sind, dass während des Schweiß- prozesses in einem oder beiden Werkstücken (2a, 2b) nichtlineare Ab- sorptionsprozesse auftreten. 7. The method according to any one of the preceding claims, characterized in that one or more pulses of the pulsed laser beam (3) have parameters which are selected so that during the welding process in one or both workpieces (2a, 2b ) non-linear absorption processes occur.
8. Laserbearbeitungsmaschine (1 ) zum Laserschweißen zweier einander überlappender Werkstücke (2a, 2b), von denen zumindest eines, insbe- sondere auch das andere, eine Transparenz von mindestens 90% bei der Laserwellenlänge aufweist, mit einem Laser (4), insbesondere UKP-Laser, zum Erzeugen eines gepulsten Laserstrahls (3), insbesondere in Form von UKP-Laserpulsen (5), mit einem Scanner (7) zum Ablenken des La- serstrahls (3) quer oder parallel zu einer Vorschubrichtung (10) und mit ei- ner Maschinensteuerung (14), die programmiert ist, den Scanner (7) der- art anzusteuern, dass einer Bewegung des Laserstrahls (3) in der Vor- schubrichtung (10) eine quer oder parallel zur Vorschubrichtung (10) ge- richtete Hin- und Flerablenkung (11 ) des Laserstrahls (3) überlagert wird. 8. Laser processing machine (1) for laser welding two overlapping workpieces (2a, 2b), of which at least one, in particular also the other, has a transparency of at least 90% at the laser wavelength, with a laser (4), in particular UKP Laser, for generating a pulsed laser beam (3), in particular in the form of UKP laser pulses (5), with a scanner (7) for deflecting the laser beam (3) transversely or parallel to a feed direction (10) and with ei - A machine controller (14) which is programmed to control the scanner (7) in such a way that a movement of the laser beam (3) in the feed direction (10) transversely or parallel to the feed direction (10) directed Hin - and Flerablenkung (11) of the laser beam (3) is superimposed.
9. Laserbearbeitungsmaschine nach Anspruch 8, gekennzeichnet durch eine Bewegungseinheit (6) zum Bewegen der beiden einander überlappenden Werkstücke (2a, 2b) in der Vorschubrichtung (10), wobei die Maschinen- steuerung (14) programmiert ist, die Bewegungseinheit (6) und den Scan- ner (7) derart anzusteuern, dass der Laserstrahl (3) in der Vorschubrichtung (10) bewegt wird und dieser Bewegung eine quer oder parallel zur Vorschubrichtung (10) gerichtete Hin- und Herablenkung (11 ) des Laserstrahls (3) überlagert wird. 9. A laser processing machine according to claim 8, characterized by a moving unit (6) for moving the two overlapping workpieces (2a, 2b) in the feed direction (10), wherein the machine control (14) is programmed, the moving unit (6) and to control the scanner (7) such that the laser beam (3) in the Feed direction (10) is moved and this movement a transverse or parallel to the feed direction (10) directed back and forth deflection (11) of the laser beam (3) is superimposed.
10. Laserbearbeitungsmaschine nach Anspruch 8 oder 9, dadurch gekenn- zeichnet, dass der Scanner (7) durch mindestens einen elektro-optischen, akusto-optischen, piezoverstellbaren oder auf mikro-elektromechanischer Systemtechnik basierenden Deflektor gebildet ist. 10. Laser processing machine according to claim 8 or 9, characterized in that the scanner (7) is formed by at least one electro-optical, acousto-optical, piezoverstellbaren or based on micro-electro-mechanical system technology deflector.
EP19717791.8A 2018-04-10 2019-04-05 Method for the laser welding of transparent workpieces, and associated laser machining tool Pending EP3774675A1 (en)

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