Method for introducing a hole into a workpiece, workpiece, method for producing a porous structure, and laser machining device

Abstract

The invention relates to a method for introducing at least one hole, in particular a through-hole (22) or a blind hole, into a workpiece (10), in which ablation structures comprising elongate grooves (14) that intersect one another are introduced into at least one surface (16, 18) of the workpiece (10) by means of at least one laser beam (12), as a result of which the hole is formed at an intersection point (20) of the grooves (14), the laser beam (12), by means of which the ablation structures are introduced into the surface (16, 18), having an elongate intensity profile in a cross-section extending in the region of the surface to be machined and / or the laser beam (12) and the workpiece (10) carrying out a lateral movement relative to one another while the ablation structures are being introduced.

Description

[0001] METHOD FOR MAKING A HOLE IN A WORKPIECE, WORKPIECE, METHOD FOR PRODUCING A POROUS STRUCTURE AND LASER PROCESSING DEVICE

[0002] The invention relates to a method for introducing at least one hole into a workpiece, a workpiece with at least one hole, a method for producing a porous structure, and a laser processing device.

[0003] It may be necessary to provide workpieces with through holes or blind holes. These holes can be created in the workpiece, for example, using a laser beam.

[0004] The object of the present invention is to provide a solution by means of which at least one hole can be made in a workpiece particularly quickly, precisely and energy-efficiently.

[0005] This problem is solved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are specified in the dependent claims, the description, and the drawings. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0006] The invention relates to a method for creating at least one hole, in particular a through hole or a blind hole, in a workpiece. The workpiece is, in particular, a foil, a substrate, or a sheet, and is preferably made of a polymer-based, ceramic, glass-based, and / or metallic material, especially homogeneous, with different layers, or as a composite material. The workpiece can, for example, be a thin titanium or stainless steel foil. A through hole is an opening that extends through the entire thickness of the workpiece. A blind hole is defined as an opening that does not completely penetrate the workpiece in the thickness direction. Thus, the blind hole does not extend through the entire workpiece in the thickness direction but terminates within the workpiece.

[0007] The method involves using at least one laser beam to create ablation structures comprising intersecting, elongated grooves into at least one surface of the workpiece, thereby forming a hole at the intersection of the grooves. In other words, the at least one laser beam is directed onto the surface of the workpiece, thereby removing material from the surface of the workpiece directly or indirectly, for example, directly by removing particles, vaporization, sublimation, and / or expulsion of molten material, or indirectly by material modification, preferably by removing the modified volume through selective etching. The ablation of material from the surface of the workpiece creates the elongated ablation structures.At each intersection point of the ablation structures, the combined material removal of the at least two intersecting grooves results in a blind hole or a through hole. Each ablation structure comprises at least one groove in the surface of the workpiece. The hole then forms at the intersection point of at least two grooves of the at least two ablation structures. The blind hole formed at each intersection point extends in the thickness direction of the workpiece over a greater proportion of the thickness direction than the respective ablation structures intersecting at the associated intersection point extend in the thickness direction outside the intersection point.

[0008] In one variant of the process, the laser beam used to create the ablation structures on the surface exhibits an elongated intensity profile in a cross-section within the area of ​​the surface being processed. The area of ​​the surface illuminated by the laser beam is referred to as the processing plane. This means that within this effective cross-section, the laser beam has an elongated intensity distribution that is not rotationally symmetric. It is possible for the cross-section of the laser beam to be elongated, for example, elliptical, and / or for the laser beam to have an intensity modulation of the beam profile such that at least one elongated intensity profile is present within the cross-section.For this process, a laser beam with an anamorphic, or non-rotationally symmetric, beam profile can be used to create the ablation structures. The effective cross-section of the laser beam can change during propagation; for example, a profile that is elongated at one point can be transformed into one that is elongated exactly perpendicular to it. The relevant factor is the effective cross-section of the laser beam on the surface being processed. The laser beam does not always have to be oriented perpendicular to the workpiece, so the effective cross-section does not necessarily correspond to a cross-section of the laser beam perpendicular to the beam direction. For example, the effective cross-section can be elongated due to a chosen angle of incidence of the laser beam, while the cross-section of the laser beam perpendicular to the beam direction is circular or rotationally symmetric.

[0009] Alternatively or additionally, the laser beam and the workpiece are designed to perform a relative lateral movement relative to each other during the application of the ablation structures. For example, a laser processing head of a laser processing device that provides the laser beam can deflect the beam on the workpiece and / or be moved laterally relative to the workpiece. This lateral relative movement means that the laser beam and the workpiece, or the laser processing head and the workpiece, are moved relative to each other in a direction parallel to the surface of the workpiece onto which the laser beam is directed for the application of the ablation structures. Thus, it is possible for the laser beam and the workpiece to be moved relative to each other while the ablation structures are being applied to the workpiece.In particular, it may be provided that the laser processing head and the workpiece are moved relative to each other while the ablation structures are introduced into the surface of the workpiece.

[0010] The relative movement of the laser beam to the workpiece thus allows for a further variation of the process, enabling the creation of elongated grooves using a rotationally symmetrical beam profile, solely through movement during the ablation process. Providing the laser beam with its elongated intensity profile across its cross-section, combined with its lateral relative movement to the workpiece, allows for particularly rapid incorporation of the elongated ablation structures into the workpiece surface. Furthermore, this incorporation of elongated ablation structures into the workpiece surface makes it especially easy and quick to create the holes at the intersections of the grooves.In particular, the intersecting ablation structures allow for the rapid creation of numerous holes in the workpiece surface with precise relative positioning. This method combines surface structuring using ablation structures with the creation of at least one hole. It also ensures that the holes are positioned within the ablation structure. This enables the rapid creation of individual holes, even under typical limitations such as inertia in a positioning system. The method reliably generates precisely positioned ablation structures and holes at high speeds, even without precise timing or high resolution in the direction of movement.The process can utilize a basic laser model, such as a continuous-wave laser or a pulsed / modulated laser beam. A scanner enables particularly rapid deflection of the laser beam, allowing the ablation structures to be introduced into the workpiece surface very quickly. A preferred direction for successively applied laser beam profiles can be rapidly adjusted between different orientations for the application of the respective ablation structures.

[0011] Within this process, through holes and / or blind holes can be created using laser processing with relative movement between the laser beam and the workpiece, utilizing intersecting ablation structures. The respective ablation structures can exhibit a pronounced preferred direction in the direction of movement of the laser beam relative to the workpiece. The preferred direction refers specifically to a principal extension direction or a longitudinal extension direction. The preferred direction of each ablation structure characterizes the direction in which the ablation structures have their greatest extent. The respective beam profiles of the laser beam for introducing the ablation structures can each be selected with an effective preferred direction acting in the direction of movement.Here, the preferred direction of the respective beam profile corresponds to the direction in which the cross-section of the laser beam as a whole, or of an intensity substructure, has its greatest extent. Alternatively or additionally, it is possible to select a laser beam with an intensity profile that is elongated relative to the workpiece in the direction of motion of the laser beam compared to an orthogonal direction. The preferred direction therefore does not necessarily have to refer to the beam profile of the laser beam as a whole—and thus the cross-sectional shape of the laser beam—but may, if necessary, refer only to a substructure of the laser beam within the intensity profile. The beam profile of the laser beam itself does not necessarily have to have a preferred direction.

[0012] Due to the relative movement of the laser beam to the workpiece, an effectively elongated effect of the laser beam profile on the workpiece surface can be achieved and / or enhanced. In cross-section, the laser beam can be rotationally symmetrical. Alternatively, the laser beam can exhibit an elongated intensity profile or an elongated cross-sectional shape in cross-section, whereby the longitudinal direction of the elongated intensity profile or the longitudinal direction of the elongated cross-sectional shape can be oblique and thus not parallel to the lateral direction of movement of the laser beam relative to the workpiece.If the laser beam has an elongated cross-sectional shape, then the longitudinal direction of this elongated cross-sectional shape can be chosen perpendicular to the relative direction of movement of the laser beam to the workpiece, in particular to achieve wide trenches with steep flanks as ablation structures, for example, using a flat top beam profile.

[0013] The described method enables the rapid creation of at least one hole, and in particular a multitude of holes, in the workpiece. Furthermore, the at least one hole can be created with exceptionally tight tolerances and with remarkable ease. In addition, the method allows for a high density of small holes in the workpiece, achieving high precision in the positioning of the holes relative to each other and to the ablation structures. Moreover, the method enables particularly effective thermal management through the rapid movement of the laser beam across the workpiece when creating entire rows of holes within a very short timeframe.In a further possible embodiment of the invention, the relative lateral movement is selected to be parallel to a longitudinal direction of the elongated grooves of the respective ablation structure. In other words, the laser beam can be moved parallel to the longitudinal direction of the groove to be created during an ongoing ablation process—and thus during the introduction of the respective ablation structure into the surface of the workpiece. By selecting the relative lateral movement of the laser beam to the workpiece as parallel to the longitudinal direction of the elongated groove to be introduced into the surface by means of the laser beam, the respective ablation structure can be introduced into the surface of the workpiece particularly easily and quickly.

[0014] In a further possible embodiment of the invention, the laser beam is aligned during movement such that a longitudinal direction of the elongated intensity profile runs parallel to a direction of movement of the laser beam across the surface of the workpiece. This allows a large material removal depth in the thickness direction to be achieved even with rapid movement of the laser beam relative to the surface of the workpiece.

[0015] In a further possible embodiment of the invention, the laser beam has a cross-section in the area of ​​the workpiece surface to be processed that is longer than it is wide. In other words, the laser beam has an elongated cross-sectional shape. It is particularly possible that the longitudinal direction of this elongated cross-sectional shape deviates by less than 10° from the relative direction of movement of the laser beam to the workpiece. This ensures that even with a rapid movement of the laser beam to the workpiece surface, the respective ablation structure can be introduced into the workpiece with a large ablation depth extending in the thickness direction. This allows the respective ablation structures to be introduced into the workpiece with a predetermined ablation depth in a particularly small number of passes.This allows for exceptionally high precision in the ablation structure, resulting in exceptionally high workpiece quality. Combined with anamorphic scanner optics, high scanning speeds and a particularly large scan field can be utilized. Aligning the laser beam with its longitudinal axis of the cross-sectional shape in the direction of relative movement enables exceptionally high quality of the ablation structures introduced into the workpiece, due to the minimal width of each groove and the high degree of symmetry of the ablation structures.

[0016] In a further possible embodiment of the invention, it is provided that, for the production of at least one through-hole, the ablation structures are introduced on opposite sides of the workpiece, whereby the through-hole is formed at an intersection point of the grooves of the different ablation structures. In other words, at least one first groove of a first ablation structure is introduced into a first surface of the workpiece, and at least one second groove of a second ablation structure is introduced into a second surface of the workpiece, wherein the first surface and the second surface are arranged on opposite sides of the workpiece.This double-sided machining process achieves exceptional efficiency, as only a very shallow material removal depth is required on each side of the workpiece compared to single-sided machining to create through-holes at the intersections. This minimal material removal depth on each side minimizes the total volume of material that needs to be removed to create the through-hole. Furthermore, machining both sides allows for a high ratio of the cross-sectional area of ​​the constrictions in the through-holes to the required area of ​​the grooves on the workpiece surfaces, into which the machining pattern is applied.Furthermore, it is possible to minimize burr formation on the workpiece surface surrounding the through-holes. Additionally, a combination of through-holes and the grooves of the machining structures on both sides of the workpiece can be achieved, with the positions of the grooves directly corresponding to the positions of the through-holes. Moreover, particularly simple thermal management is possible when machining the workpiece from both sides. If the machining structures are applied to both sides of the workpiece simultaneously, a particularly uniform heat input into the workpiece is achieved, thus significantly reducing the risk of warping.In a further possible embodiment of the invention, each of the ablation structures comprises several parallel linear grooves, and the grooves of different ablation structures differ with respect to the orientation of their longitudinal direction and / or their width and / or their length and / or their depth and / or their aspect ratio and / or their spacing from one another and / or their cross-sectional geometry. The respective linear grooves can extend straight or odd, in particular with at least one curvature, in a plane spanned by the unmachined surface of the workpiece in which the respective ablation structure has been introduced. The longitudinal direction is the direction in which the grooves have their greatest extent. The length of the respective grooves runs in the longitudinal direction of the respective grooves.The depth of each groove runs in the thickness direction of the workpiece, with the thickness direction being perpendicular to the workpiece surface that is irradiated with the laser beam to create the at least one ablation structure. The width of each groove runs perpendicular to its depth. The width of the groove describes the shortest distance between the edges of the workpiece that define the groove on the workpiece surface. The spacing between the grooves refers to the shortest distance between the grooves associated with a common ablation structure within the plane defined by the workpiece surface. An aspect ratio is the height-to-width ratio of microstructures. In process engineering, the aspect ratio is understood as the ratio of the depth or height of a structure, in this case the grooves, to its lateral extent.The aspect ratio, as used here, is the ratio of a groove's depth to its lateral extent. The larger the aspect ratio and the smaller the absolute size of the grooves, the more difficult it is to create them in the workpiece surface. By selecting the specific groove design, particularly regarding the orientation of the longitudinal direction and / or width and / or length and / or depth and / or aspect ratio and / or spacing between grooves in a material removal structure and / or cross-sectional geometry of the grooves, the position and shape of the holes to be created at the groove intersections can be determined.

[0017] In a further possible embodiment of the invention, it is provided that several different ablation structures are successively applied to the same surface of the workpiece in a sequence, overlapping each other at least partially. Because the different ablation structures overlap each other at least partially, their grooves can be intersected at at least one intersection point. In particular, it is provided that at least a first groove of a first ablation structure intersects at least a second groove of a second ablation structure, thereby forming the hole at the intersection point. Because the ablation structures are applied to the same surface of the workpiece, only one access point of the workpiece, corresponding to this surface, is required for the laser beam.Furthermore, by introducing the ablation structures into the same surface, blind holes can be created as holes in the workpiece. Additionally, within this process, another surface of the workpiece, which is arranged differently from the surface, particularly opposite the surface into which the ablation structures have been introduced, can be retained, apart from any through-holes that may be formed. With a transparent workpiece design, and with irradiation of the workpiece from one side, it is possible to introduce ablation structures onto opposing surfaces of the workpiece by ablation from the beam exit side.

[0018] In particular, it is intended that the narrower the grooves of each ablation structure are, the later in the application sequence that structure is introduced into the surface. If the grooves of two ablation structures to be introduced into the surface differ, the structure with the finer grooves is introduced after the structure with the coarser grooves and / or with a shallower ablation depth. This allows for exceptionally high process control. Furthermore, it ensures a particularly high level of precision in the ablation structures introduced into the workpiece, as the finer structures are not affected by subsequent machining during the application of the coarser structures.Overall, this allows for particularly high efficiency in the application of the ablation structures, as finer grooves are typically applied with reduced average power and / or efficiency compared to coarser grooves. Applying coarser grooves, and thus grooves with greater width, length, and / or depth, requires the removal of more material from the workpiece than applying comparatively finer grooves. The application sequence describes the order in which the respective ablation structures are applied to the workpiece.

[0019] In a further possible embodiment of the invention, the respective machining depths of the machining structures are selected such that a through-hole is formed only at the intersection points where at least three grooves overlap. This means that, for the introduction of the respective machining structures, a depth of the respective grooves is selected such that the through-hole is formed only at points where three grooves of the respective machining structures overlap, due to the summed machining of the three grooves. The respective machining structures can be introduced into the surface of the workpiece with different machining directions and / or with the same machining direction.It is possible that, with more than two overlapping ablation structures, the machining direction of several ablation structures and / or grooves is selected to be parallel to each other, whereby the geometry of the individual ablation structures and / or grooves may differ, for example, with regard to their width or depth. Alternatively or additionally, a differing orientation of the respective longitudinal extension directions of the grooves to be crossed for the production of the through-hole, with more than two differing directions, allows for particularly good control of respective areas of the workpiece that must be kept free of through-holes, as well as a particularly precise arrangement of the respective through-holes in the workpiece.For example, the respective longitudinal directions of the grooves can be rotated at an angle of 60° around a perpendicular on the workpiece surface, thus simplifying the implementation of a hexagonal arrangement of multiple through holes. Furthermore, this design of the machining depths allows through holes to be formed only at the intersection points where at least three grooves meet. This makes it particularly easy to create complex structures in which blind holes and through holes can be combined, and / or through holes with different cross-sections and / or different positions of their narrowest cross-section relative to the thickness direction of the workpiece can be created.For example, at least two of the through-holes can have different distances from each other to the originally unmachined surface of the workpiece with respect to their narrowest flow cross-section, and thus be arranged at different depths within the workpiece in the thickness direction. The respective narrowest cross-section typically runs perpendicular to the thickness direction of the workpiece and describes the cross-section of the respective through-hole with the smallest extent and / or area. This narrowest cross-section represents, for example, a constriction of flow for a fluid that flows through the respective through-hole when the workpiece is used as intended.

[0020] In a possible further development of the invention, the ablation structures are integrated into the workpiece such that a groove of a first ablation structure intersects at least two grooves of a second ablation structure. The length of a first groove of a first ablation structure is thus selected such that this first groove intersects several second grooves of the second ablation structure. This allows a large number of small holes with precise relative positions to be easily integrated into the workpiece. A particularly high hole density can therefore be achieved in the workpiece. Furthermore, by providing long grooves, high ablation rates can be achieved with rapid beam movement and without switching the laser. By selecting narrow, elongated grooves for the first ablation structure, a dense arrangement of holes formed at the respective intersection points can be created.Even if the first groove of the first ablation structure is chosen with a width greater than the center-to-center distance of the second grooves of the second ablation structure intersecting the first groove, distances between the resulting holes can be achieved in the longitudinal direction of the first groove that correspond to the center-to-center distance of the second grooves. This allows for efficient and productive drilling of the holes in the workpiece even with limited resolution of the machining in the scan direction.

[0021] In a possible further development of the invention, it is provided that the ablation structures are introduced into at least one surface of the workpiece by means of a rotator optic – which can also be referred to as a rotary optic. The rotator optic is configured to provide the laser beam in a rotating direction. This means that the supplied laser beam is oriented with its beam direction obliquely or perpendicular to an axis of rotation around which the laser beam rotates. The beam direction extends radially outwards from the axis of rotation. Using the rotator optic, the grooves can be introduced into the workpiece particularly quickly and with particular precision.The invention further relates to a workpiece with at least one hole, in particular a through hole or a blind hole, wherein the workpiece has intersecting ablation structures comprising elongated grooves introduced into at least one surface of the workpiece by means of at least one laser beam, the hole being arranged at an intersection point of the grooves. In particular, it is provided that exactly one hole is provided at each intersection point. If the workpiece has several holes, then each of the holes is arranged at a separate intersection point. In particular, the workpiece is produced in a method as already described in connection with the inventive method for introducing at least one hole into a workpiece.In particular, the workpiece is a foil, a substrate or a sheet, and is made of a polymer-based, ceramic, glass-based and / or metallic material, especially homogeneous, with different layers or as a composite material. The workpiece could, for example, be a thin titanium or stainless steel foil.

[0022] The invention further relates to a method for producing a porous structure, in which, for the production of the porous structure, several workpieces, as already described in connection with the workpiece according to the invention, and which in particular have been produced in a method as already described in connection with the method according to the invention for introducing at least one hole into a workpiece, are stacked on top of each other in a stacking direction and joined together in a material-bonded manner. The porous structure is thus produced by stacking a plurality of workpieces, each with at least one hole, in particular a plurality of holes, on top of each other in a stacking direction.By creating the porous structure through stacking the individual workpieces, into which precisely defined holes have been introduced at predetermined positions during the process, the porous structure can be produced with exceptional precision and reproducibility. Varying the design of the individual workpieces and the stacking sequence allows for a high degree of flexibility regarding the flexibility achievable within the porous structure. Variations in the workpiece design include, for example, the workpiece thickness, geometry, orientation, and / or arrangement of the ablation structures and / or the material itself. Films without ablation structures can also be integrated during stacking. The multiple workpieces can be joined together using diffusion welding. For workpieces containing glass, bonding can be used, if necessary.Thermally assisted or in conjunction with surface activation, the workpieces can be bonded together. Alternatively or additionally, they can be bonded together by adhesive bonding. Alternatively or additionally, laser welding can be used to bond the workpieces together at the edges without creating ablation structures.

[0023] Because the through-holes are located at the respective grooves, the workpiece enables particularly precise flow management of the fluid flowing through the through-holes and in the grooves. Within the porous structure encompassing the multiple workpieces, this allows for exceptionally precise fluid flow management, both in the stacking direction and perpendicular to it.

[0024] In a possible further development of the invention, the porous structure is configured to be used as a filter, in an electrochemical device, in a catalyst device, in a reverse osmosis device, or in a heat exchanger. The filter is a device for separating media, for example, solids from a gas or liquid stream. Because the porous structure can be manufactured with particular precision according to predetermined properties by stacking the respective components, reliable and predetermined filtration of a gas and / or liquid stream can be achieved using the filter. The electrochemical device is configured to convert chemical energy into electrical energy. The catalyst device is a device comprising a catalyst.A catalyst is a substance that increases the rate of a reaction by lowering the activation energy of a chemical reaction without being consumed itself. An osmosis device is designed to carry out an osmotic process. In the natural sciences, osmosis refers to the directed flow of particles through a selectively or semipermeable barrier. A heat exchanger is a device by which thermal energy can be transferred from one fluid stream to another.

[0025] In a possible further development of the invention, it is provided that, for the production of the porous structure, at least one film without ablation structures, wherein the film may be free of openings or may include at least one opening, is stacked in the stacking direction onto at least one of the workpieces. Thus, an integration of films without ablation structures, with or without cutouts, can be achieved for enhanced flow control.

[0026] The invention further relates to a laser processing device configured to provide at least one laser beam with an elongated intensity profile in its cross-section perpendicular to a beam direction and to align it in the beam direction onto a workpiece, whereby elongated, intersecting ablation structures comprising grooves can be introduced into at least one surface of the workpiece by means of the laser beam, whereby a hole, in particular a through hole or a blind hole, is formed at an intersection point of the grooves of the ablation structures. The laser processing device is thus configured to be used within the framework of the method according to the invention for introducing the at least one hole into a workpiece. In particular, the laser processing device comprises a basic model laser, in particular a continuous-wave laser or a pulsed or modulated laser.The laser processing device can include anamorphic optics, which can be configured as a scanner. This allows for particularly high resolution in one axis of the processing zone and enables a large working area at high scanning speeds in the other axis. The laser processing device can be configured to perform highly dynamic scanning in a large working area while maintaining high resolution in one axis. The ablation process for groove generation is carried out, in particular, by scanning in a single pass or in multiple passes. This means that each groove of the respective ablation structure is generated in one or more passes. The laser processing device can be configured to process multiple grooves and / or ablation structures in parallel in a single pass.

[0027] In a possible further development of the invention, the laser processing device comprises anamorphic optics and / or a multi-beam interference device, wherein the anamorphic optics or the multi-beam interference device are configured to provide the laser beam with the extended intensity profile. The astigmatic optics can be configured to convert the laser beam into an anamorphic shape. The multi-beam interference device can be configured to perform direct laser beam interference structuring. Here, respective intensity maxima or the extended intensity profile can be generated by means of dual-beam interference, wherein the laser beam in the processing zone exhibits a spatially periodically modulated intensity profile.Here, spatial modulation in a spatial direction with a particularly short period can be implemented, resulting in elongated intensity profiles. This spatially periodically modulated intensity profile can also be achieved without or with only a slight preferred direction of the envelope, meaning that the envelope is rotationally symmetric, only slightly elongated, or has another shape, but a preferred direction of the individual intensity maxima is present. The intensity maxima are therefore not rotationally symmetric or point-symmetric to each other. For example, two rectangular tophat profiles can be superimposed, resulting in intensity profiles of the same maximum intensity and length for individual laser partial beams superimposed in the processing plane.In principle, in multi-beam interference, the laser beam is split into at least two partial laser beams, which then cause intensity modulation in the superposition region, with the period decreasing as the difference angle increases. The partial laser beams are recombined in the processing plane—and thus in a processing zone—resulting in intensity modulation there. Outside the processing zone, the partial laser beams diverge again, and the superposition, and therefore the modulation, disappears.

[0028] Further features of the invention may become apparent from the following description of the figures and from the drawings. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0029] The drawing shows in:

[0030] Fig. 1 shows a schematic top view of a workpiece into which intersecting ablation structures comprising elongated grooves are introduced by means of a laser beam, with holes forming at the respective intersection points of the grooves;

[0031] Fig. 2 shows a normal projection of the workpiece in a first embodiment with a plurality of holes;

[0032] Fig. 3 shows a normal projection of the workpiece in a second embodiment with a plurality of holes;

[0033] Fig. 4 shows a normal projection of the workpiece in a third embodiment with a plurality of holes;

[0034] Fig. 5 shows a schematic top view of areas of the workpiece irradiated by means of a laser beam to create the grooves;

[0035] Fig. 6 shows a normal projection of the workpiece in a fourth embodiment with a plurality of holes;

[0036] Fig. 7 shows a normal projection of the workpiece in a fifth embodiment with a plurality of holes;

[0037] Fig. 8 shows a normal projection of the workpiece in a sixth embodiment with a plurality of holes;

[0038] Fig. 9 shows a normal projection of a porous structure formed by stacking two workpieces with a multitude of holes;

[0039] Fig. 10 shows a schematic perspective view of a laser processing device by means of which elongated groove-enclosing ablation structures are introduced into the workpiece;

[0040] Fig. 11 shows a schematic top view of the workpiece in a seventh embodiment, in which elongated grooves comprising ablation structures are introduced; Fig. 12 shows a schematic top view of the workpiece in an eighth embodiment, in which elongated grooves comprising ablation structures are introduced;

[0041] Fig. 13 shows a schematic longitudinal section of the workpiece into which elongated grooves are made on one side using a rotator optic;

[0042] Fig. 14 shows a schematic longitudinal section of the workpiece, into which elongated grooves are cut on both sides using respective rotator optics; and

[0043] Fig. 15 shows a schematic longitudinal section of two workpieces into which elongated grooves are simultaneously introduced using a rotator optic.

[0044] Identical or functionally equivalent elements are marked with the same reference symbols in the figures.

[0045] Figure 1 shows a workpiece 10 into which ablation structures comprising intersecting, elongated grooves 14 have been introduced into at least one surface 16, 18 by means of at least one laser beam 12. Holes 22 are arranged at the respective intersection points 20 of the grooves 14. For clarity, only some of the intersection points 20 and some of the through holes 22 are labeled with their corresponding reference numerals. Alternatively, instead of forming through holes 22, a blind hole can be arranged at at least one intersection point 20. In this case, the workpiece 10 is a foil made of a metallic material.

[0046] The workpiece 10 was produced, in particular, by means of a process in which the intersecting, elongated grooves 14 ablation structures were introduced into at least a first surface 16 of the workpiece 10 by means of at least one laser beam 12. It is possible that each of the ablation structures has one or more elongated grooves 14. The at least one laser beam 12, by means of which the grooves 14 were introduced into the first surface 16, can have an elongated intensity profile in a cross-section perpendicular to a beam direction. Alternatively or additionally, it can be provided that the laser beam 12 and the workpiece 10 perform a relative lateral movement with respect to each other during the introduction of the ablation structures.The relative lateral movement is parallel to a longitudinal direction of the respective grooves 14 produced in the surface 16, 18 of the workpiece 10 by means of the laser beam 12. The laser beam 12 is oriented, particularly when moving relative to the workpiece 10, such that a longitudinal direction of the elongated intensity profile of the laser beam 12 is parallel to a direction of movement of the laser beam 12 as it moves across the surface 16, 18 of the workpiece 10. In particular, the laser beam 12 has a cross-section perpendicular to its beam direction, which is longer than it is wide. This means that the laser beam 12, in its cross-section perpendicular to the beam direction and / or in its projection onto the surface 16, 18 of the workpiece 10, has an elongated cross-section, in particular an elliptical cross-section.The intersecting ablation structures can be introduced into the same surface 16, 18, in particular the first surface 16, or into different surfaces 16, 18 of the workpiece 10, and thus into both the first surface 16 and the second surface 18 of the workpiece 10. It is specifically provided that the first surface 16 and the second surface 18 are arranged on opposite sides of the workpiece 10. If the ablation structures are introduced into the opposite surfaces 16, 18 of the workpiece 10, then through holes 22 are formed at the respective intersection points 20 of the grooves 14. If the intersecting ablation structures are introduced into the same side 16, 18 of the workpiece 10, then either through holes 22 or blind holes can form at the respective intersection points 20.

[0047] As can be seen particularly well in Fig. 1, each of the ablation structures comprises several parallel linear grooves 14. The parallel grooves 14 of each ablation structure thus maintain a distance of at least substantially the same along their entire length from the respective immediately adjacent groove 14 of the same ablation structure. It is possible that the grooves 14 of the different ablation structures differ with respect to the orientation of their longitudinal direction and / or their width and / or their length and / or their depth and / or their aspect ratio and / or their distances from the immediately adjacent groove 14 of the same ablation structure and / or their cross-sectional geometry.If several different ablation structures are to be introduced successively into the same surface 16, 18 of the workpiece 10 in an introduction sequence, overlapping each other at least in some areas, then it is provided that, the less wide and / or deep the respective grooves 14 of the respective ablation structure are, the later in the introduction sequence the respective ablation structure is introduced into the surface 16, 18 of the workpiece 10.

[0048] It is possible that the respective removal depths of the grooves 14 of the removal structures are chosen such that the respective through holes 22 only occur at intersection points 20 where three grooves 14, in particular three grooves 14 of three different removal structures, intersect.

[0049] As can be seen in Fig. 1, for the particularly efficient creation of a large number of closely spaced holes, it is provided that a first groove 14 of a first of the ablation structures intersects at least two grooves 14 of a second of the ablation structures at respective intersection points 20. In the present case, it is provided that a first groove 14 of the first ablation structure intersects several grooves 14, and thus in particular more than two grooves 14 of the second ablation structure, at respective intersection points 20.

[0050] To produce a porous structure 24, it can be provided that, as shown in Fig. 9, several workpieces 10, which have been provided with at least one hole by introducing intersecting ablation structures, are stacked on top of each other in a stacking direction. Furthermore, it is provided that the stacked workpieces 10 are bonded together by means of at least one laser beam 12. This produced porous structure 24 can be used in particular as a filter, in an electrochemical device, in a catalyst device, in an osmosis device, or in a heat exchanger.

[0051] To provide the laser beam 12 with an elongated cross-section, a laser processing device 26 with anamorphic optics can be used. To provide the laser beam 12 with an elongated intensity profile in the cross-section, regardless of whether it has a rotationally symmetrical or an elongated cross-section, a laser processing device 26 comprising a multi-beam interference device, in particular a dual-beam interference device, can be used.

[0052] Figures 2, 3, 4, 6, 7, 8, and 9 show normal projections of the respective workpieces 10 in different embodiments in European representation. Figures 2 and 3 show the respective workpieces 10 into which a plurality of through holes 22 have been machined by machining the first surface 16 of the workpiece 10 on one side. The machining features grooves 14 with a longitudinal orientation rotated 90° relative to each other, machined into the first surface 16 of the workpiece 10. The elongated grooves 14 may have been machined into the workpiece 10, in particular, using a line optic scanner. If a rotator optic is used, the grooves 14 may have been machined into the surface 16 of the workpiece 10 with a slight curve.The grooves 14 can be introduced into the first surface 16 of the workpiece 10 in a continuous process without increased positioning requirements. The first grooves 14 of the first ablation structure can be introduced into the first surface 16 using an efficient process, whereas the second grooves of the second ablation structure can be introduced into the first surface 16 while avoiding melt flow, at least during the breakthrough phase. Due to the one-sided processing of the workpiece 10 in Figures 2 and 3, access to the second side of the workpiece 18 for the laser beam 12 is not necessary. The second surface 18 remains largely intact, with the exception of the respective through-holes 22. This allows for good cleaning and a reduced risk of clogging at the constriction of the respective through-holes 22 near the unprocessed second surface 18, for applications such as filters.Furthermore, a particularly large surface area of ​​the workpiece 10 can be achieved by structuring the first surface 16, while simultaneously maintaining a small area fraction but a high density of the through-holes 22. This is advantageous for use in conjunction with a catalyst layer, for example, for electrolysis or a fuel cell. This fine structure on the first surface 16 of the workpiece 10 can embed itself in a proton exchange membrane or a catalyst-coated membrane.

[0053] The workpieces 10 shown in Figures 2 and 3 differ only in the depth of the respective grooves 14 cut into the first surface 16. For clarity, only some of the grooves 14 are labeled with their corresponding reference numerals. In the workpiece configuration shown in Figures 2 and 3, the first grooves 14 of the first ablation structure and the second grooves 14 of the second ablation structure each have the same shape in a cross-section perpendicular to the longitudinal direction. This means that the first grooves 14 of the first ablation structure and the second grooves 14 of the second ablation structure differ in their geometry only in the orientation of their longitudinal direction.

[0054] In the embodiment of the workpiece 10 shown in Fig. 4, the grooves 14 of the different ablation structures are formed in different surfaces 16, 18 of the workpiece 10. This means that the first grooves 14 of the first ablation structure are formed in the first surface 16 of the workpiece 10, and the second grooves 14 of the second ablation structure are formed in the second surface 18 of the workpiece 10. Furthermore, the first grooves 14 of the first ablation structure differ from the second grooves 14 of the second ablation structure in their respective cross-sections, which are perpendicular to the longitudinal direction of the respective grooves 14. The first grooves 14 of the first ablation structure and the second grooves 14 of the second ablation structure are oriented with their longitudinal direction rotated by 90° relative to each other.The smaller the width of the respective grooves 14, the shallower their depth can be. The abrasive structure comprising the finer grooves 14 can be introduced into the workpiece 10 after the abrasive structure comprising the coarser grooves 14. By selecting the depth of the abrasive structures, the cross-sectional area of ​​the through-openings can be controlled. Alternatively or additionally, the position of the constrictions relative to the surface can be adjusted.

[0055] Because the grooves 14 of the different ablation structures differ in their cross-section perpendicular to the longitudinal direction, the resulting through-holes 22 at the intersection points 20 of the ablation structures can have a cross-section that deviates from a rotationally symmetric shape, in this case an elliptical cross-section. Particularly fine grooves 14 can be achieved by using direct laser interference structuring (DLIP), especially by means of dual-beam interference, such that the intensity profile of the laser beam 12 is modulated with a period in the range of a single-digit or small double-digit multiple of the wavelength. Here, a modulation direction of the intensity profile of the laser beam 12 is selected, in particular perpendicular to a scan direction.As with the use of multispot valves, several grooves 14 of a removal structure can be processed simultaneously during a scan, whereby the simultaneously processed grooves 14 in particular do not overlap and unprocessed surface of the workpiece 10 remains between the grooves 14.

[0056] Figure 5 shows the cross-sectional area of ​​the laser beam 12 that creates the grooves 14 in the workpiece 10 as depicted in Figure 4. It can be seen that the laser beam 12 has a different cross-section for creating the first grooves 14 of the first ablation structure than for creating the second grooves 14 of the second ablation structure.

[0057] Figure 6 shows a workpiece 10 into which elongated grooves 14 of respective ablation structures are produced on one side, and thus only on the first surface 16. The respective intersecting grooves 14 are arranged with their longitudinal directions rotated 90° relative to each other about a thickness direction of the workpiece 10. The thickness direction runs along the shortest path from the first surface 16 to the second surface 18. In the representation shown in Figure 6, through-holes 22 are formed at the respective intersection points 20. To generate the respective through-holes 22 with a reduced number of passes, a particularly long exposure time can be achieved by using laser beams 12 with elongated cross-sections in the direction of movement, which produce the grooves 14 in the first surface 16 of the workpiece 10, and / or by using particularly long pulses or pulse groups when using pulsed laser beams 12.

[0058] On the laser exit side, the second surface 18 is intact except for the through-holes 22. In the embodiment shown in Fig. 6, no grooves 14 extending through multiple through-holes 22 are provided on the laser entry side—and thus on the first surface 16. Instead, a continuous residual grid of the first surface 16 remains. Therefore, synchronization of the laser emission with the movement of the laser beam 12 is necessary for the creation of the holes, not only at a boundary of a processing area. The requirements for this synchronization decrease with increasing length of the respective grooves 14. However, the required period also increases with increasing length of the respective grooves 14, which reduces the achievable hole density. As shown in Fig.As can be detected in Fig. 7, interrupted grooves 14 with multiple intersection points 20 can be implemented in the scan direction, resulting in a higher density of holes compared to single intersection points. On the other hand, the limited longitudinal extent of the grooves on the first surface 16 allows for a particularly large remaining unprocessed area, which facilitates the easy stacking of multiple workpieces 10 and their joining via their respective flat interfaces. In the embodiment shown in Fig. 7, grooves 14 with limited length are provided, with through holes 22 forming at the respective intersection points 20. In the workpiece 10 shown in Fig. 7, all grooves 14 are incorporated into the first surface 16 of the workpiece 10. Apart from the through holes 22, the second surface 18, which is located on the laser exit side, remains intact.The first surface 16 can have machining regions and non-machining regions, wherein the surface is divided into machining regions and non-machining regions by interrupting and omitting grooves 14. In the non-machining regions, the first surface 16 is intact. In particular, due to the non-machining regions, the first surface 16 has continuous ribs on the laser entry side. In the embodiment of the workpiece 10 shown in Fig. 7, it is provided that first grooves 14 of the first ablation structure intersect several second grooves 14 of the second ablation structure. In particular, it is provided that each groove 14 of one of the ablation structures intersects three grooves 14 of the other ablation structure at respective resulting intersection points 20. It should be emphasized that in Fig. 7, the grooves 14 of the ablation structures are arranged so densely compared to their width that, in contrast to Fig.1, 2, 3 no unmachined surface areas, which can be described as columns, remain between directly adjacent grooves 14, nor do unmachined surface areas, which can be described as webs, remain between directly adjacent grooves 14 as in Figs. 4, 8, 9. Such unmachined surface areas, which are advantageous for contacting with other components and especially for stacking, and in which the workpiece 10 still has an original thickness after machining, are achieved in Fig. 7 by non-machining regions. In particular, webs are also advantageous for the mechanical stability of the workpiece 10 and can alternatively or additionally be ensured by non-machining regions, even when ablation structures are introduced on both the first and second sides, but especially when ablation structures are introduced only on the first or only on the second side. In the case shown in Fig.In the embodiment shown in Fig. 8, the respective ablation structures are incorporated into the opposing surfaces 16 and 18 of the workpiece 10. This means that the first ablation structure is incorporated into the first surface 16 and the second ablation structure is incorporated into the second surface 18 of the workpiece 10. The first grooves 4 of the first ablation structure and the second grooves 14 of the second ablation structure have the same cross-section, perpendicular to the longitudinal direction. Incorporating the grooves 14 into opposing sides of the workpiece 10 offers potential for process optimization, increased efficiency, and improved media management. When using the workpiece 10 shown in Fig. 8 as a component in a stacked arrangement, continuous webs that remain permanently in place can serve as flat supports and contact surfaces.The respective continuous grooves 14 enable good media management in a stack of workpieces 10.

[0059] Figure 9 shows a porous structure 24 produced by stacking several workpieces 10 in a stacking direction. The workpieces 10 stacked in the stacking direction can have different configurations. In particular, it is provided that the first of the workpieces 10 is positioned with its first surface 16 against the second surface 18 of the second workpiece 10 for stacking in the stacking direction. This allows for the creation of graded structures. In other words, a gradually changing porosity of the porous structure 24 can be achieved by stacking different workpieces 10. Furthermore, support functionality can be achieved by joining the respective workpieces 10 by diffusion welding and / or by selecting a specific thickness for each workpiece 10.By selecting a length for the respective grooves 14, media management can be carried out within the porous structure 24 in a lateral direction in areas without through holes 22.

[0060] When stacking, unlike in Fig. 9, films with ablation structures only on the first or only on the second side can be used as an alternative or supplement. Films on the outer side of the stack can have ablation structures on either the side facing the stack or the side facing away from it. Alternatively or additionally, films with non-machined regions or films entirely without ablation structures can also be used in the stack. In this context, it should be emphasized that the grooves 14 of the ablation structures, particularly in combination with non-machined regions and / or stacking, allow for flow control both in the stacking direction and perpendicular to it, thus facilitating integrated fluid flow management.The combination of workpieces having ablation structures with unprocessed foils and / or foils having cutouts, preferably produced by laser cutting, expands the potential of the inventive method using stacking.

[0061] If the workpiece 10 consists of films with through holes 22, these can be stacked in the stacking direction to serve as filters or as permeable carrier substrates, as an alternative to porous sintered nonwovens or woven components. Laser processing of films offers the advantage that unprocessed areas can be left outside the processing areas to create stable and sealing connections. Furthermore, regions with differing or varying properties can be created with good spatial control. Flexible geometries and arrangements of processing regions on the workpiece can be selected, especially in combination with variations in the ablation structures in different regions or within a single region.Modulating the laser beam's power synchronized with the desired processing geometry allows for influencing a residual grid or processing geometry.

[0062] Figure 10 shows a schematic side view of a laser processing device 26 while the laser processing device 26 introduces ablation structures into the workpiece 10. For the introduction of the ablation structures, the workpiece 10 is positioned relative to the laser processing device 26 and, to introduce a plurality of ablation structures, preferably during the introduction of an ablation structure, is moved laterally in a direction of movement 28. A relative movement between the laser processing direction and the workpiece during the introduction of an ablation structure, particularly under continuous movement, as occurs, for example, in roll-to-roll processing processes, is referred to below as "on-the-fly processing". In this case, the laser processing device 26 is provided to include a scanner optic 30 by means of which an input beam 32 is deflected.This deflected input beam 32 is focused onto the surface of the workpiece 10 to be processed by means of an anamorphic focusing device 34. The laser processing device 26 further comprises a propellant slot nozzle 36 and a suction nozzle 38. The laser processing device 26 is configured to process the surface of the workpiece 10 in a linear processing zone 40.

[0063] The laser processing device 26 is configured to process the workpiece 10 using an ablative laser processing method. Ablative laser processing methods benefit from improved removal of material removal products. These products are quickly and safely removed from the processing zone 40, thereby improving the laser process and preventing health hazards and contamination of the laser processing device 26.

[0064] Figures 11 and 12 show an example of a line removal with angle a to the belt feed direction v. r As shown, the workpiece 10 is machined roll-to-roll under continuous strip feed. Material is removed across the machining width Bb in the feed direction v. r within a scan time t s In a single pass along a continuous line at an angle α (0° < α < 180°) to the strip feed direction, using a beam profile with LA as the preferred direction, where LA represents the long axis. This results in a workpiece-specific machining length Bi = Bb / sin(α). To compensate for the strip feed B s =v r xts is enhanced by an additional KA scan movement with a scan area SKA=B s *sin(a) the scanning direction and speed v sThe system is adapted, with KA standing for the short axis. Using anamorphic optics, an elliptical beam profile can be generated from a rotationally symmetric input beam in the processing region. The long axis of the ellipse lies in, or forms, the preferred LA direction. This preferred direction, linked to the anamorphic optics, is typically aligned parallel to the longitudinal extension direction of the ablation structures. The main scan direction of a scanner in the laser processing device lies in the LA direction. The LA direction is the one with the smaller numerical aperture. KA stands for short direction, where the short direction is perpendicular to the long direction. In addition to an LA scan component, the laser processing device also has a KA scan component. The KA scan component is used, among other things, for positioning the ablation structures in the transverse direction.On the other hand, the KA scan component is used to compensate for the relative movement between the scanner and workpiece 10. In total, the components of the LA scan movement and the KA scan movement exhibit exactly the speed of the relative movement in the direction of motion. The KA direction is the one with the higher numerical aperture.

[0065] For processing across the full processing width, an LA scan area SLA=Bi+BsXcos(a)=Bb / sin(a)+B is used. sxcos(a) is used. The working area must be selected to be larger according to the steel profile dimensions. The scan area and the working area must be adjusted if the processing zone is not defined with respect to the beam profile center. If necessary, the beam profile can be adapted to the angle, for example, by limiting it with a parallelogram. To limit the KA scan width and also the offset of successively scanned processing lines, the LA scan speed VLA must be adjusted relative to the belt speed: VLA=VrX[Bb / (BsXsin(a))+cos(a)]=Bb / (tsXsin(a))+v r xcos(a). Since the processing strength depends on the scan speed, the parameters v r , Bb, B sand to select a suitable value and adjust further process parameters (repetition frequency, LA profile extent). For a ≥ 90°, a > 90° is preferably chosen to reduce the required scan speed and the working field size compared to a > 90°. A parameter selection that ensures an effective scan direction v is advantageous with regard to ensuring the z-position. s orthogonal to the belt feed direction v r This results in (a>90°, ß=90°), so that the z-position can only be ensured in a short area overall and in the feed direction.

[0066] For ablation, suitable laser parameters are selected, particularly with regard to wavelength, power, intensity, and / or, in the case of pulsed lasers, fluence and pulse duration. The ablation depth is then controlled by the number of pulses acting at a given location during a pass and / or an exposure time. For this purpose, the effective profile lengths of the respective grooves 14, the scan speed, and, if necessary, a repetition frequency are adjusted accordingly. If the ablation and feed directions are orthogonal, the scan area and the working field SKA=B result. Sand SLA=Bb=Bi. A working field corresponding to the scan field plus the beam shape extent in the respective direction is required. The device is particularly suitable in conjunction with beam profiles larger than KA extent PKA, for example for removing several grooves 14 whose spacing significantly exceeds the groove width. Such an application requires a large KA working field extent aKA=PKA compared to the extent of a single unshaped partial beam profile. +SKA. This also applies if processing is not performed under relative motion, with or without the use of an KA scan area. Figures 13 to 15 show respective workpieces 10 in longitudinal sections, with the respective grooves 14 being produced in the respective workpiece 10 by means of a rotator optic. If the laser processing device 26 includes the rotator optic, highly dynamic system control is possible. The rotator optic is a machine base with high-precision axes. The rotator optic can be used in conjunction with CW lasers, in particular also with highly repetitive pulsed lasers, preferably ultrashort pulsed lasers, in this case in the near-infrared or UV range. The rotator optic enables pulse-accurate partial beam modulation / deflection.

[0067] Figure 13 shows one-sided machining of the workpiece 10 with relative movement of the rotator optics to the workpiece 10. With each rotation of the rotator optics, two intersecting grooves 14 are produced by rotating the rotator optics on a radius R. Different angles are achieved for the leading and trailing machining operations by varying the distance D of the rotation axis from the centerline of the workpiece 10. By selecting D = R x sin(45°), an angle of 45° to the centerline is achieved, and an angle of 90° is achieved between the grooves 14. A smaller change in the groove angles and groove spacing across a workpiece width can be achieved by selecting a larger ratio of R to W, but this leads to reduced utilization.

[0068] Figure 14 shows how the workpiece 10 is processed with two optics under relative motion. The laser beam is switched such that ablation structures are introduced only on one crossing of the workpiece during a rotation, unlike in Figure 13. Two rotation axes, shifted symmetrically opposite to the center of the workpiece 10, reduce the variation in the angle of difference between the grooves 14. As shown in Figure 14, the workpiece 10 can be processed on both sides using the two rotator optics. Figure 15 shows how two workpieces 10 are processed simultaneously with one rotator optic, resulting in higher utilization compared to Figure 14. This process involves processing the two workpieces 10 under relative motion with respect to the rotator optic.Thus, two workpieces 10 can be moved parallel to each other and relative to the rotator optics, and thereby processed simultaneously using the rotator optics. It is advantageous to process the first grooves 14 in a first pass and the second grooves 14 in a second pass. At least one of the workpieces 10 can be turned over in between, so that single-sided or double-sided processing using a single rotator optics is possible for creating the intersecting ablation structures.

[0069] The use of basic model lasers at wavelengths in the near-infrared, visible, or ultraviolet spectral range, particularly in the range of 1020 to 1100 nanometers, especially in the range of 510 to 550 nanometers, 340 to 360 nanometers, or 255 to 275 nanometers, enables particularly high overall efficiency due to the high efficiency of the beam source, excellent focusability, and increased absorption at short wavelengths. For the application of the ablation structures, a laser with an average power in the range of 100 to 4000 watts, especially in the range of 200 to 2000 watts, and / or a peak power of at least 2000 watts is used. This peak power applies particularly in conjunction with pulsed lasers and especially when using frequency-converted lasers operating at low average power.Laser processing can be performed by dynamically modulating the average laser power, allowing modulation of 10% to 90% of the applied laser power within less than 50 microseconds, particularly less than 5 microseconds, and preferably less than 500 nanoseconds. This rapid modulation, combined with fast beam movement and good synchronization, enables precise control of the ablation structures, especially at the start and end of each groove. Furthermore, the rapid modulation allows for control of heat accumulation even with moderate beam movement, while maintaining a peak power level suitable for the process, both with continuous-wave lasers and with highly repetitive pulsed lasers.

[0070] In this process, a continuous-wave laser and / or a pulsed laser is used, wherein the pulsed laser has, in particular, an achievable repetition frequency of at least 500 kHz, in particular at least 2 MHz, and in particular more than 10 MHz. The use of a continuous-wave laser or a laser with a high repetition frequency allows for a dense arrangement of the through-holes 22 even under rapid beam movement. In particular, for pulsed lasers, the laser beam 12 is pulsed with a pulse duration of less than 200 nanoseconds, in particular less than 100 picoseconds. The energy density of the laser power on the workpiece 10 is, in particular, 0.3 to 30 J / cm². 2 , especially 1 to 10 J / cm² 2A combination of different laser parameters from a single beam source and / or multiple beam sources to generate the intersecting ablation structures, particularly in different process phases in temporal and / or spatial sequence, enables an efficient ablation process without subsequent finishing. Therefore, a continuous-wave (CW) laser or a highly pulsed, preferably ultrashort-pulsed, laser in the near-infrared or ultraviolet range can be used for this process.

[0071] To optimize process efficiency and machining quality, the inventive method offers the advantage of first removing a large portion of the material volume in a first machining step using an efficient and / or rapid ablation process, which is typically associated with a considerable heat input, for example, significant melting. In a second machining step, it is then advantageous to remove the remaining volume using a fine ablation process, associated with reduced heat input, for example, using ultrashort laser pulses. Here, the ablation structure, which has the finer and / or shallower grooves 14, can be introduced into the workpiece 10 using a fine ablation process. Both the fine ablation and rapid ablation processes can also be performed from the same side.It is also possible to combine a one-sided rapid material removal process with a fine material removal process in a parallel longitudinal direction, particularly with finer grooves and / or reduced groove spacing in the fine material removal process. Typically, a large portion of the groove depth achieved by superimposing the material with the subsequent fine material removal is removed in the rapid material removal process. For example, a fast and efficient process can first be used to remove a large portion of the material volume, such as by melt ejectation.

[0072] Subsequently, a precision process can be carried out on the remaining volume to be removed, for example as a cold ultrashort pulse process. In particular, the precision process can be used to create the through-hole 22 at the respective intersection point 20.

[0073] In particular, process parameters are selected that promote productive and / or efficient rapid material removal by utilizing controlled heat accumulation for at least 50% of the total material volume to be removed, in combination with subsequent fine material removal. Continuous grooves 14 enable particularly efficient melt removal. Furthermore, process parameters can be used that promote high-quality fine material removal while avoiding disruptive heat accumulation in fine material structures and / or when generating through-holes 22 following rapid material removal. Melt removal alone might not provide the required quality for the through-holes 22. The material structures can be generated in multiple passes, particularly by adjusting the process parameters between each pass.This allows for improved quality, particularly with process-phase-adapted parameters, through multipass processing. Furthermore, multiple passes enable adaptive process control by adjusting the number of passes or by adjusting parameters in subsequent passes. Laser processing can be performed with an intensity profile of the laser beam 12 generated by dual-beam interference. The two interfering partial beams span a plane in the area of ​​the workpiece 10, the normal of which lies in a plane defined by the preferred direction of the structures—and thus the longitudinal direction of the grooves 14—and the surface normal of the workpiece 10. Dual-beam interference allows for the generation of beam profiles that are extended in one spatial direction and exhibit intensity distributions with steep flanks and small extent in the spatial direction perpendicular to it.When larger beams intersect perpendicular to the preferred direction, a periodic intensity profile of the laser beam 12 is formed, which allows several line-like structures to be processed simultaneously. This beam profile of the laser beam 12 can also be maintained over a larger area when the beams propagate, compared to beam profiles of the same lateral extent with standard focusing.

[0074] The laser processing of the workpiece 10 can take place in a protective and / or process gas atmosphere and / or also under fluid support, in particular using gaseous, liquid and / or mixed fluids, during the entire processing process and / or adapted to the respective process phases.

[0075] Laser processing under a protective and / or process gas atmosphere allows for the reduction of reactions with atmospheric oxygen, without compromising electrical performance or contact reliability. Furthermore, wettability can be selectively controlled spatially through laser processing in a process gas atmosphere. Processing the workpiece 10 in a fluid, particularly a liquid, automatically establishes a protective gas atmosphere, and heat generated during the process can be dissipated directly. The respective fluids or fluid mixtures can be used for cooling and material removal. The workpiece 10 can preferably be processed in a flowing fluid, especially within a laser beam-workpiece interaction zone.The workpiece can thus be processed in a controlled environment, protecting it from contamination, binding and removing the removed material, ensuring the workpiece is protected from particles, and allowing harmful process gases to be contained. Furthermore, heat generated during the process can be dissipated directly. Chemical reactions can be suppressed or selectively promoted by choosing the appropriate gas. The wettability of the workpiece 10 can be spatially selectively influenced by laser processing in a process gas atmosphere.

[0076] The workpiece 10 can be machined in an elongated machining zone with a comparatively small transverse extent. Due to the elongated machining field or zone, combined with its small orthogonal extent, the flow can be directed very locally and precisely close to the machining area. Maintaining a predetermined distance between the workpiece 10 and the machining optics, or maintaining a predetermined position of the beam profile in the beam propagation direction, is only ensured in the largely linear machining zone 40. This allows for the machining of a workpiece 10 clamped onto a guide roller. In the machining region where the ablation structures are to be introduced into the workpiece 10, the workpiece 10 has a material thickness in the range of 10 to 500 micrometers, particularly in the range of 20 to 200 micrometers.Within the scope of the process, a foil, in particular a metallic foil, with a thickness of 10 to 500 micrometers, and especially with a thickness of 20 to 200 micrometers, can be processed as workpiece 10. Within the scope of the process, a foil coated on one or both sides, in particular a metal foil, with a thickness of 5 to 200 micrometers and a coating thickness of 0.1 to 100 micrometers can be processed as workpiece 10. Within the scope of the process, a coated foil can thus be processed, whereby a coating structure suitable for through holes 22 can be created.

[0077] Within the scope of this process, a workpiece 10 can be machined which, in a machining region where the ablation structures are to be introduced into the workpiece 10, has a reduced material thickness compared to other regions of the workpiece 10. This allows for the provision of a support structure of the workpiece 10 prior to the machining process. The support structure can be created by tapering the workpiece 10 in certain areas and / or by additively applying support structures and / or by applying a film to the workpiece 10. As shown in Fig. 7, for example, there would be no unmachined column-shaped or rib-shaped areas extending to the original surface between the grooves. However, unlike in Fig. 7, the tapering would occur beforehand and not by introducing the ablation structures.

[0078] The processing can be carried out with relative movement between a processing optic of the laser processing device 26 and the workpiece 10. This enables continuous processing in a region of the workpiece 10 traversing the processing zone 40 of the optic. The processing of the workpiece 10 can be carried out using an anamorphic scanner optic which has a first preferred direction of lower numerical aperture on the workpiece side and a second preferred direction of higher numerical aperture orthogonal to it, wherein the magnitude of the angular deviation of the first preferred direction deviates by a maximum of 10°, in particular by less than 5°, from the relative direction of movement of the laser beam 12 to the workpiece 10. Such a line optic scanner enables a high scanning speed and a large working field in the direction of the first preferred direction and a high resolution in the direction of the second preferred direction.An anamorphic scanner optic can be used in which the numerical aperture of the second preferred direction exceeds that of the first preferred direction by at least a factor of 2, in particular by at least a factor of 5, and in particular by at least a factor of 10. The anamorphic scanner optic can be used with a scanning device comprising a component in the first preferred direction and an additional component in the second preferred direction. These components can be selected relative to each other such that, under relative movement of the processing optic to the workpiece 10, a relative movement direction of the laser beam 12 to the workpiece 10 can be set with only an insignificant deviation from the first preferred direction of the optic. The two components can be controlled independently and synchronously with each other. This allows for compensation of the relative movement.Successive processing of the workpiece 10 can be carried out with the longitudinal extension directions of the beam profile and the intensity profile of the laser beam 12 oriented differently from the relative direction of movement between the optics and the workpiece 10, whereby the angular difference between the direction of movement and the respective longitudinal extension directions is selected to be greater than 30°. If the deviation of the longitudinal extension direction of the beam profile from the direction of movement and the longitudinal extension direction of the intensity profile from the direction of movement is less than 10° and the longitudinal extension directions are oriented in opposite directions relative to the direction of movement, the angular difference between the direction of movement and the longitudinal extension directions is selected to be greater than 45° in each case.Here, the orientation of the longitudinal direction is chosen to be as symmetrical as possible to the direction of movement, with a component in the direction of movement that is not too large. The scan direction, in particular, has a component in the opposite direction to the relative direction of movement. If the longitudinal direction is not oriented perpendicular to the direction of the relative movement, then it has a component in the direction of movement. This can be determined by vector addition. It is intended that the angle of the longitudinal direction (a) relative to the direction of the relative movement – ​​the direction of movement – ​​does not deviate too much from 90°. In a line-optical scanner, the LA direction is chosen to be parallel to the longitudinal direction. The greater the angular deviation, the longer the working area required to cover the same processing width.With the line optic scanner, one scan unit can be oriented in the LA direction and another scan unit in the KA direction. If the scan direction is chosen such that it has a component "against" the direction of movement (Fig. 11, β > 90°), then a lower scan speed and scan length are sufficient to achieve the same scan speed and scan length on the workpiece than if the scan direction has a component in the direction of movement (Fig. 12, β < 90°).

[0079] Within the framework of this method, sequential processing can be carried out using two anamorphic scanner optics arranged either opposite to the direction of movement of the workpiece 10 or one behind the other in the direction of movement. This is particularly suitable for processing workpieces 10 unwound from a roll, especially for roll-to-roll processing. A rotator optic can be used for rapid beam deflection. A crossed alignment of the longitudinal directions of the respective grooves 14 can be achieved using a rotator optic moving rapidly along a circular path. Any preferred direction can be rotated along with the beam to achieve a minimal effective dimension of the respective through-hole 22. The ablation structures can thus be introduced along a circular path. If a beam profile with a preferred direction is used, it should be aligned as tangentially as possible to this circular path at each point.If the beam shape were imprinted in front of the rotator optics, it would then have to be rotated to match. Therefore, it can be designed so that the preferred direction is imprinted directly on the rotating optics in such a way that it rotates along with them.

[0080] Within the framework of this process, roll-to-roll processing of thin films or thin materials of less than 200 micrometers can be carried out such that the ablation structures are introduced using a workpiece 10 placed on a guide roller. As can be seen in the extensions to the statements in Figures 11 and 12, by appropriately selecting the speeds for the relative movement and the scan speed for workpiece-related ablation directions a > 90°, an effective scan angle β of 90° can be achieved, thus ensuring a straight line parallel to an axial direction of the guide roller and maintaining the distance between the laser processing device and the workpiece surface. A substantially linear working field offers improved processing width compared to a working field with a comparable area but larger transverse dimensions, with regard to process and plant technology.The small lateral dimension facilitates process gas flow and the removal of swarf. Furthermore, the small lateral dimension facilitates adherence to z-position tolerances. If a longitudinal insertion direction perpendicular to a strip feed direction of the workpiece 10 is selected, then the preferred direction of the intersecting longitudinal insertion direction for a right-angled arrangement of the through holes 22 is oriented parallel to the strip feed direction. This makes it virtually impossible to cover an entire strip width with a single optic. Therefore, an arrangement deviating from the parallel or perpendicular orientation of the optic's longitudinal insertion direction to the strip feed direction is recommended.The longitudinal direction or arrangement of the grooves 14 in roll-to-roll structuring can be in an angular range α of 30° to 60° or 120° to 150°, particularly in an angular range α of 40° to 50° or 130° to 140° with respect to the direction of movement 28 of the workpiece 10 relative to the laser processing device 26. A symmetrical solution is achieved with an orientation of the optics at an angle of 45° to the strip feed direction. Angular ranges α > 90° and / or scan angle ranges β of 90° to 150°, particularly between 90° and 120°, are preferred. Multispot profiles with spots offset from each other in the longitudinal direction can be used, wherein the spots successively process the same ablation structure, in particular the same groove 14, during beam movement.This allows for increased efficiency per pass, or a comparable effect at increased speed, and / or improved quality. Spots operating within the same ablation structure can exhibit differing parameters, particularly different modulation over time, power output, pulse energy, repetition frequency, spot diameters, and / or parallel offset in the direction of movement. Thus, the method enables process-phase-adapted control of the material input by multiple spots within an ablation structure or groove in a single pass.

[0081] These process-phase-adapted parameters of the individual spots allow for the processing of multiple process phases in a single pass. By varying the modulation of individual spots, ablation structures, particularly grooves 14, with flank extensions in the scan direction significantly shorter than the length of the multispot profile can be achieved with overall elongated multispot profiles. It is even possible to achieve flank extensions on the order of magnitude of the extent of a subspot.

[0082] Alternatively or additionally, multiple grooves can be created simultaneously using multispot profiles that are separated by a distance greater than the width of a groove 14 in the direction perpendicular to the relative movement direction, in particular by an integer multiple of the center distance of adjacent grooves 14. This allows for the simultaneous structuring of multiple grooves 14 to increase performance and productivity. If the spot spacing is chosen to be greater than the desired groove 14 spacing, this enables a process with reduced interaction between the simultaneously created grooves 14 and minimizes heat accumulation effects due to subsequent gap filling.Alternatively or additionally, the distance and relative speed can be coordinated so that, during successive passes, the creation of individual grooves is initiated with one or more spots, while other spots continue processing grooves that have already been pre-worked. Spots operating within the same ablation structure can exhibit differing parameters, in particular, different modulation over time, different power, different pulse energy, different repetition frequency, different spot diameters, and / or different parallel offsets in the direction of movement. Thus, the method allows for process-phase-adapted control of the material creation by multiple spots in a single pass.

[0083] A sequential processing procedure can be implemented, combining relative motion processing and scan processing in a temporally sequential manner. The relative motion processing is performed in a processing direction largely corresponding to the relative motion of the workpiece 10 to the optics, using a multi-spot profile with spots offset perpendicular to the relative motion direction. The scan processing, on the other hand, is performed with an anamorphic scanner optics with a relative beam movement to the workpiece 10 that deviates from the relative motion.Here, a relative motion machining operation is performed with a relatively slow relative movement between the optics and the workpiece 10, for example in a roll-to-roll application, with a low duty cycle for the power application to individual spots. This is achieved by switching the laser beam 12 to the individual spots in a time-shifted manner and / or simultaneously applying power to several spots at a high power increase, so that machining with low heat accumulation can be carried out as a cold process. A linear machining zone 40 can be used for this purpose. The scan machining operation is performed with a fast scanning motion and can be performed upstream of this cold machining operation with controlled heat accumulation.

[0084] An intermediate or subsequent subtractive or modified laser processing of the workpiece 10 and / or an additively generated structure with a short or ultrashort pulse laser with a pulse duration of less than 100 nanoseconds, in particular less than 100 picoseconds at a fluence of less than 20 J / cm² 2Laser processing can be used to create fine structural details, for smoothing, cleaning, removing oxide layers, and / or checking wettability. Often, for a large part of laser processing, an efficient and / or cost-effective process is sought, but this does not yet offer the desired quality. Post-processing can achieve an overall economical process that meets the quality requirements. For example, in large-area, high-throughput laser processing, it is difficult to guarantee a suitable process or protective gas atmosphere. Post-processing can include the creation of LIPPS (Limited Induction Surfaces) at laser parameters close to an ablation threshold.Laser processing can be carried out, in particular, using an intensity distribution of the laser beam 12 that is elongated in the longitudinal direction of the grooves 14, especially by moving the beam profile of the laser beam 12 relative to the workpiece 10 in the longitudinal direction of the respective grooves 14. Due to the large extent of the beam profile of the laser beam 12, an increased effect can be achieved at high feed rates. This allows for a particularly large ablation front with a small angle. In conjunction with a line optic scanner, an enlarged scan field and a particularly high scan speed can be achieved in the longitudinal direction of the grooves 14 at the same angular velocity.

[0085] A system-technical implementation of laser processing of thin materials, especially thin titanium foils, can be achieved using a polygon scanner and / or an anamorphic line optics scanner, particularly in a roll-to-roll process. This allows for exceptionally high productivity. Simultaneously, heat can be distributed evenly over a large area. An elongated, slim processing zone 40 enables a combination of high-throughput laser processing with an advantageous geometry for the removal of ablation products via nozzles for gas or fluid flow, as well as a gap in a support in the area of ​​the through-holes 22. The workpiece 10 can be processed from both sides with the surface of the workpiece 10 vertically oriented and the workpiece moving downwards. Material removal via nozzles in the direction of gravity can then be achieved, thereby reducing the risk of contamination of the optics.Even without turning the workpiece 10 over, this avoids processing the underside of the workpiece 10 in a way that is unfavorable with regard to contamination.

[0086] The process can be carried out with adaptive process control to ensure high yield by analyzing and evaluating the through-holes 22 and / or the structural depth of the respective grooves 14 during the ongoing process, particularly using optical diagnostics, and using this data to adjust process parameters. In this process, laser processing in a processing area can be combined with a multitude of through-holes 22 produced by laser perforation and a surface structuring with a longitudinal direction, particularly one that extends continuously through the processing area. A separate process allows for the combination of single-pulse or multi-spot drilling with single-pass line engraving. Overall, the invention demonstrates how laser processing of a film for combined structuring and drilling can be designed.

[0087] REFERENCE MARK LIST

[0088] 10 workpieces

[0089] 12 Laser beam

[0090] 14 groove

[0091] 16 first surface

[0092] 18 second surface

[0093] 20 Intersection point

[0094] 22 Through hole

[0095] 24 porous structure

[0096] 26 Laser processing device

[0097] 28 Direction of movement

[0098] 30 Scanner optics

[0099] 32 Input beam

[0100] 34 anamorphic focusing device

[0101] 36 propellant slot nozzle

[0102] 38 Suction nozzle

[0103] 40 linear machining zone

[0104] Bb processing width

[0105] Bi processing length

[0106] B s Belt feed

[0107] D distance

[0108] VLA LA scan speed t s Scan time

[0109] SKA scan area

[0110] SLA scan range v s Scan direction v r Belt feed direction a angle

[0111] R radius

Claims

PATENT CLAIMS 1. Method for introducing at least one hole, in particular a through hole (22) or a blind hole, into a workpiece (10), wherein ablation structures comprising intersecting, elongated grooves (14) are introduced into at least one surface (16, 18) of the workpiece (10) by means of at least one laser beam (12), whereby the hole is formed at an intersection point (20) of the grooves (14), wherein the laser beam (12), by means of which the ablation structures are introduced into the surface (16, 18), has an elongated intensity profile in a cross-section extending in the area of ​​the surface to be processed, and / or the laser beam (12) and the workpiece (10) perform a relative lateral movement when introducing the ablation structures.

2. Method according to claim 1, characterized in that the relative lateral movement is selected parallel to a longitudinal extension direction of the elongated grooves (14) of the respective ablation structure.

3. Method according to claim 1 or 2, characterized in that the laser beam (12) is aligned during movement such that a longitudinal extension direction of the elongated intensity profile runs parallel to a movement direction of the laser beam (12) moving over the surface (16, 18) of the workpiece (10).

4. Method according to one of the preceding claims, characterized in that the laser beam (12) has a cross-section extending in a region of the surface (16, 18) to be processed which is longer than it is wide.

5. Method according to one of the preceding claims, characterized in that the ablation structures are used to produce at least one through hole (22). on opposite sides of the workpiece (10), whereby the through hole (22) is formed at a crossing point (20) of the grooves (14) of the different ablation structures.

6. Method according to one of the preceding claims, characterized in that each of the ablation structures comprises several parallel linear grooves (14) and the grooves (14) of different ablation structures differ with respect to the orientation of their longitudinal extension direction and / or their width and / or their length and / or their depth and / or their aspect ratio and / or their distances to each other and / or their cross-sectional geometry.

7. Method according to one of the preceding claims, characterized in that several different ablation structures are successively introduced into the same surface (16, 18) of the workpiece (10) in an introduction sequence, at least partially overlapping each other, wherein the narrower the grooves (14) of the respective ablation structure are, the later in the introduction sequence the respective ablation structure is introduced into the surface (16, 18).

8. Method according to one of the preceding claims, characterized in that the respective removal depths of the removal structures are selected such that a respective through hole (22) is formed only at the intersection points (20) where at least three grooves (14) overlap.

9. Method according to one of the preceding claims, characterized in that the ablation structures are introduced into the workpiece (10) such that a groove (14) of a first ablation structure crosses at least two grooves (14) of a second ablation structure.

10. Method according to one of the preceding claims, characterized in that The ablation structures are introduced into at least one surface (16, 18) of the workpiece (10) by means of a rotator optic.

11. Workpiece (10) with at least one hole, in particular a through hole (22) or a blind hole, wherein the workpiece (10) has intersecting ablation structures comprising elongated grooves (14) introduced into at least one surface (16, 18) of the workpiece (10) by means of at least one laser beam (12), wherein the hole is arranged at an intersection point (20) of the grooves (14).

12. Method for producing a porous structure (24) in which, for producing the porous structure, several workpieces (10) according to claim 11, which in particular have been produced in a method according to one of claims 1 to 10, are stacked on top of each other in a stacking direction and are joined together in a materially bonded manner.

13. Method according to claim 12, characterized in that the porous structure (24) is configured to be used as a filter or in an electrochemical device or in a catalyst device or in an osmosis device or in a heat exchanger.

14. Method according to claim 12 or 13, characterized in that for producing the porous structure (24) at least one film without ablation structures, wherein the film may be free of openings or may include at least one opening, is stacked in the stacking direction onto at least one of the workpieces (10).

15. Laser processing device (26) which is configured to provide at least one laser beam (12) with an elongated intensity profile in a cross-section extending in the area of ​​the surface to be processed and to align the beam direction towards a workpiece (10), wherein intersecting ablation structures comprising at least one elongated groove (14) are created in at least one surface (16, 18) of the workpiece (10) by means of the laser beam (12). can be introduced, thereby forming a hole, in particular a through hole (22) or a blind hole, at a crossing point (20) of the grooves (14).

16. Laser processing device (26) according to claim 15, characterized by an astigmatic optic and / or a multi-beam interference device, which are configured to provide the laser beam (12) with the elongated intensity profile.

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