Welding mask for a laser welding device for creating a welded join, laser welding device for creating a welded join, and method for creating a welded join

Abstract

A welding mask (26) for a laser welding device (10) for creating a welded join between a foil stack (12) and an electrical conductor (14) by means of a laser beam (16).

Description

[0001] Title: Welding mask for a laser welding device for producing a weld joint, laser welding device for producing a weld joint and method for producing a weld joint

[0002] Description

[0003] The invention relates to a welding mask for a laser welding device for producing a welded joint, a laser welding device for producing a welded joint, and a method for producing a welded joint. WO 2021 / 043418 A1 discloses a welding device and a method for welding at least two components together. The welding device has an ultrasonic welding device and a laser welding device. The welding device is configured to weld the two components together in a first area using the ultrasonic welding device and, during the ultrasonic welding process, to weld the two components together in a second area, which is smaller than the first area and which is arranged within and / or adjacent to an outer boundary of the first area, using the laser welding device.For this purpose, the ultrasonic welding device can include an ultrasonic sonotrode and / or an anvil, which have a through-hole within the first area. The.

[0004] The laser welding device can be configured to direct a laser beam through the through-hole onto the second area on the two components in order to additionally weld the two components together by laser welding.

[0005] The invention is based on the objective of providing a welding mask for a laser welding device for producing a welded joint, providing a laser welding device for producing a welded joint and providing a method for producing a welded joint, each of which reduces or completely avoids the occurrence of processing defects, in particular welding defects of the welded joint, and enables the production of a welded joint that has high strength.

[0006] The invention solves this problem by providing a welding mask with the features of claim 1, a laser welding device with the features of claim 9, and a method with the features of claim 10. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0007] A welding mask according to the invention is suitable for a laser welding device for producing a weld between a stack of foils and an electrical conductor using a laser beam. The welding mask has a contact surface for contacting the stack of foils and a plurality, for example 4, 6, 9, 16, 25 or 36, of recesses. The plurality of recesses are suitable for directing the laser beam onto the stack of foils through the recesses for the purpose of producing the weld. Each recess extends from an inlet opening of the welding mask to an outlet opening of the welding mask. The distance between two adjacent inlet openings is less than 5 times, in particular 3 times, 2 times or 1.5 times, the diameter of one of the two adjacent inlet openings.Additionally or alternatively, the distance between two adjacent outlet openings is less than 5 times, in particular 3 times, 2 times or 1.5 times, the diameter of one of the two adjacent outlet openings.

[0008] Advantageously, such a selected distance between two adjacent inlet and / or outlet openings can enable the creation of a stable, reliable weld joint with the melting of a small volume. In particular, this allows the weld joint to be created with minimal heat input into the foil stack and / or electrical conductor, thereby reducing or completely preventing cracking that can occur after the weld joint is created during cooling due to shrinkage. Therefore, the welding mask can reduce or completely prevent the occurrence of processing defects, especially welding defects in the weld joint.

[0009] Furthermore, such a selected distance between two adjacent inlet openings and / or outlet openings can advantageously enable the production of a welded joint with high strength, so that no further connection, for example in the form of an ultrasonic welding joint, is required to attach the foil stack to the electrical conductor.

[0010] Furthermore, it is advantageous to produce a welded connection with such a selected distance between two adjacent inlet openings and / or outlet openings that the film stack, in particular all films of the film stack, and the electrical conductor are connected to each other with an electrical connection that has a low electrical resistance.

[0011] The stack of foil can be attached to the electrical conductor, in particular only, by means of the welding connection.

[0012] The film stack can consist of films, particularly electrode films, arranged one above the other. For example, the film stack can consist of 10 to 120 films, particularly 40 to 100 films, overlapping each other. Each film can have a thickness ranging from 5 pm (micrometers) to 50 pm, particularly 6 pm to 20 pm.

[0013] The foil stack can be formed from metallic foils. Each foil can be formed from a material containing aluminum, copper, or lithium. Preferably, the foil stack and / or each foil can be formed from pure aluminum, pure copper, or pure lithium. Pure aluminum can be understood to mean an aluminum material of alloy group 1000 and / or a material with a weight fraction of at least 99% aluminum. Pure copper can be understood to mean copper Cu-OF or copper Cu-ETP. Additionally or alternatively, pure copper can be understood to mean a material with a weight fraction of at least 99% copper. Pure lithium can be understood to mean a material with a weight fraction of at least 99% lithium.

[0014] The foil stack can be referred to as an electrode foil stack. The foil stack can be suitable for forming a battery cell, in particular a lithium-ion battery or a solid-state battery. The foil stack can be a foil stack of a battery cell.

[0015] The electrical conductor can be a current collector for a battery cell. The electrical conductor can be made of the same material as the foil stack. Alternatively, the material of the electrical conductor and the material of the foil stack can differ; for example, one of the two materials can be pure copper and the other pure aluminum. The electrical conductor can have a thickness of 0.1 mm to 2 mm, particularly 0.3 mm to 0.5 mm.

[0016] Creating the welded connection between the foil stack and the electrical conductor can be understood as joining the foils of the foil stack to each other and joining the foil stack to the electrical conductor.

[0017] The laser beam can be pulsed or continuous-wave. With a continuous-wave laser beam, the weld seam can be continuous, particularly as a linear seam. With a pulsed laser beam, the weld seam can have interruptions. In particular, a weld seam produced by a pulsed laser beam can be a step weld or a pulsed weld. These interruptions can result in reduced heat input into the film stack.

[0018] The laser beam can be a single-mode laser beam or a multi-mode laser beam. The laser beam can have a diffraction coefficient M.2 of 2 or less, particularly in the range of 1 to 1.4. Alternatively, the laser beam can have a diffraction coefficient M. 2 exhibiting a value greater than 4. Preferably, the laser beam can have a Gaussian intensity profile or a top-hat-shaped intensity profile.

[0019] The laser welding device can include a focusing lens for focusing the laser beam onto the stack of foils. The laser beam can be a laser beam focused onto the stack of foils. By focusing the laser beam onto the stack of foils, a laser spot can be formed on the stack. The laser beam can be focused onto the stack of foils such that it strikes the stack with a beam parameter product in the range of 0.38 mm*mrad (millimeters*milliradians) to 16 mm*mrad. Preferably, the laser beam strikes the stack with a beam parameter product in the range of 0.4 mm*mrad to 0.6 mm*mrad.The laser beam can be focused on the stack of foils in such a way that, if the laser beam is a single-mode laser beam, it strikes the stack of foils with a beam parameter product of 0.6 mm*mrad, or, if the laser beam is a multi-mode laser beam, it strikes the stack of foils with a beam parameter product of less than or equal to 8 mm*mrad, in particular 4 mm*mrad.

[0020] The laser beam can be focused onto the stack of foils such that the beam diameter of the laser beam on the foil stack has a value in the range of 10 pm to 300 pm, in particular 30 pm to 50 pm or 50 pm to 170 pm. If the laser beam is a single-mode laser beam, the beam diameter of the laser beam on the foil stack can have a value in the range of 30 pm to 50 pm. If the laser beam is a multi-mode laser beam, the beam diameter of the laser beam on the foil stack can have a value in the range of 50 pm to 170 pm.

[0021] The laser beam can be a bundle of several individual beams, in particular 2, 3, 4, or 6. The laser beam bundle can be focused onto the stack of foils such that each beam forms a focus on the stack. During the welding process, the beams can rotate around an optical axis of the laser beam bundle. This allows for uniform, rapid, and large-area melting.

[0022] The laser beam can have a wavelength in the range of 800 nm (nanometers) to 1200 nm, particularly 1020 nm to 1080 nm. Preferably, the laser beam can have a wavelength of 1030 nm, 1064 nm, or 1070 nm. Alternatively, the laser beam can have a wavelength in the range of 400 nm to 450 nm or 500 nm to 550 nm. Preferably, the laser beam can have a wavelength of 515 nm. Advantageously, a laser beam with a wavelength of 515 nm can be particularly suitable for producing the laser weld in copper.

[0023] The laser beam can have a power output in the range of 0.1 kW (kilowatts) to 6 kW, particularly 0.2 kW to 2 kW. The laser beam can be formed by superimposing two partial beams that differ in their beam diameters. The optical axes of the two partial beams can be the same after superposition. Advantageously, this can stabilize a vapor capillary (keyhole) that occurs during the welding process.

[0024] The laser beam can be formed by means of a first partial beam and a second partial beam, wherein the first partial beam has a circular intensity profile and the second partial beam has an annular intensity profile. The beam diameter of the first partial beam can be smaller than the inner diameter of the second partial beam. The first partial beam can be surrounded by the second partial beam. In other words, the second partial beam can define an interior region, with the first partial beam located within this interior region.

[0025] The weld connection between the foil stack and the electrical conductor can be created by guiding the laser beam across the foil stack. The laser beam can be guided across the foil stack at a speed ranging from 0.2 m / min (meters per minute) to 60 m / min, and in particular from 10 m / min to 30 m / min. Speed ​​can be understood as the velocity at which the laser beam is focused on the foil stack relative to the foil stack.

[0026] The contact surface can be designed as a flat surface. The contact surface can be designed as a continuous surface. Alternatively, the contact surface can be formed from multiple surface sections. Each surface section can be designed separately from the other surface sections. The contact surface can be designed to be pressed against the stack of films to create the weld.

[0027] Each cutout can be designed as a through-hole or channel. Each cutout can provide a passage for the laser beam to pass through the welding mask. The cutouts can form a perforation of the welding mask.

[0028] The welding mask can have 5 to 10 cutouts.

[0029] The welding mask can have a first side and a second side opposite the first. The contact surface and the exhaust openings can be located on the first side. The inlet openings can be located on the second side. In other words, the inlet openings can be located on a side of the welding mask opposite the contact surface. The exhaust openings and the contact surfaces can be located on the same side of the welding mask.

[0030] Each exit opening can define a welding area on the film stack, especially when the welding mask is pressed against the film stack to create the weld. The laser beam can be guided over the welding area, thereby creating a weld. The weld can be formed by the weld points. The weld can be formed by a number of weld points equal to the number of cutouts, the number of entry openings, and / or the number of exit openings.

[0031] Each inlet and / or outlet can have a center point. Each center point can be a geometric centroid, particularly in the form of a centroid of the area, of the inlet and / or outlet.

[0032] The distance between two adjacent inlet openings can be understood as the distance between the two centers, in particular the centroids, of the two adjacent inlet openings. The distance between two adjacent outlet openings can be understood as the distance between the two centers, in particular the centroids, of the two adjacent outlet openings.

[0033] The diameter of an entrance opening can be defined as the length of a straight line passing through the center of the opening, connecting two opposite points on one edge of the opening, and parallel to a line segment connecting the centers of two adjacent entrance openings. This allows the diameter of the entrance opening to be determined regardless of its shape, such as rectangular or oval.

[0034] The diameter of an outlet opening can be defined as the length of a straight line passing through the center of the outlet opening, connecting two opposite points on one edge of the outlet opening, and parallel to a line segment connecting the centers of two adjacent outlet openings. This allows the diameter of the outlet opening to be determined regardless of its shape, such as rectangular or oval.

[0035] The distance between two adjacent entrance openings can be less than 5 times, in particular 3 times, 2 times or 1.5 times, the smaller diameter of the two adjacent entrance openings.

[0036] The distance between two adjacent entrance openings can be greater than 0.5 times, in particular 1 times, the diameter, in particular the smaller diameter, of the two adjacent entrance openings.

[0037] The distance between two adjacent entry openings can be in the range of 3 mm to 15 mm, in particular 5 mm to 10 mm.

[0038] All entry openings can have the same diameter. All entry openings can be identical in design, in particular, they can have the same shape.

[0039] The distance between two adjacent outlet openings can be less than 5 times, in particular 3 times, 2 times or 1.5 times, the smaller diameter of the two adjacent outlet openings.

[0040] The distance between two adjacent outlet openings can be greater than 0.5 times, in particular 1 times, the diameter, in particular the smaller diameter, of the two adjacent outlet openings.

[0041] The distance between two adjacent outlet openings can be in the range of 3 mm to 15 mm, in particular 5 mm to 10 mm.

[0042] All outlet openings can have the same diameter. All outlet openings can be identical in design, in particular, they can have the same shape.

[0043] Another aspect of the welding mask is that the cutouts divide the weld into individual weld points, specifically segmenting them. Due to the arrangement of the cutouts, the weld points can be spaced apart in such a way that heat input into the film mask during the welding process is reduced and / or evenly distributed. This minimizes shrinkage of the film stack and the electrical conductor caused by heat input during welding, thus reducing or completely preventing the formation of cracks or other processing defects that can result from excessive shrinkage. As a result, all films in the stack can be mechanically securely connected to the electrical conductor, and the electrical resistance between the conductor and the film stack can be low.

[0044] In this further development of the welding mask, each exit opening is adjacent to the contact surface. Advantageously, this allows the exit openings to be made as small as possible, enabling the welding mask to contact the film stack as close as possible to the weld point and thus transmit the force required to press the film stack as close as possible to the weld points within the film stack. This significantly reduces gaps between individual sheets of film in the stack, thereby minimizing or even completely preventing the occurrence of cracks. As a result, a high-quality weld can be produced.

[0045] Each exit opening can be surrounded by the contact surface.

[0046] In a further development of the welding mask, each exit opening has a surface area of ​​less than 150 mm². 2Advantageously, this allows the exit openings to be small. Furthermore, it is advantageous that contact forces can be introduced into the film stack particularly close to a weld point to reduce gaps between the individual sheets. In particular, each exit opening can have an area of ​​approximately 10 mm². 2 up to 50 mm 2 exhibit.

[0047] In a further development of the welding mask, each inlet opening has an area that is at least 10%, and in particular 20%, larger than the area of ​​the outlet opening, which is connected to the inlet opening via a recess. Advantageously, this allows the laser beam to pass through the recesses, significantly reducing the risk of the laser beam grazing the welding mask. Furthermore, this advantageously results in fewer spatter particles adhering to the mask. The area of ​​each inlet opening can be less than twice, and in particular 1.3 times, the area of ​​the outlet opening, which is connected to the inlet opening via a recess.

[0048] In a further development of the welding mask, the cross-sectional area of ​​each recess decreases from the inlet opening to the outlet opening. Each recess can be conical, at least partially, and in particular completely. Advantageously, this allows the laser beam to pass through the recesses and strike the stack of foil at a larger angle of incidence.

[0049] In a further development of the welding mask, each inlet and / or outlet opening is circular, oval, particularly elliptical, or rectangular. Advantageously, this allows the shape of the inlet and / or outlet openings to be adapted to the shape of the weld joint, especially the shape of the individual weld points. By adapting the shape, particularly small outlet openings can be achieved, thereby significantly reducing gaps between the individual films.

[0050] In a further development of the welding mask, the mask has a plurality of protrusions, for example, 4, 6, 9, 16, 25, or 36. Each protrusion defines an outlet opening and forms a section, in particular a surface section, of the contact area. Advantageously, this allows for a particularly high contact pressure near the weld point. The contact area can be formed, in particular, solely by the protrusions. Each protrusion can completely surround an outlet opening. The number of protrusions can equal the number of outlet openings. Each outlet opening can be associated with a protrusion.

[0051] In a further development of the welding mask, each protrusion has a height of at least 0.5 mm. Each protrusion can have a height of up to 2 mm, in particular 1 mm.

[0052] A laser welding device, in particular a laser welding machine, according to the invention is designed to produce a welded joint between a stack of foils and an electrical conductor using a laser beam. The laser welding device comprises a laser beam source for generating the laser beam, a beam deflection device for directing the laser beam onto the stack of foils, and a welding mask as previously described. The beam deflection device is designed to direct the laser beam through the openings for the purpose of producing the welded joint.

[0053] The laser welding device can be designed to press, in particular to compress, the welding mask against the stack of foil in order to create the welded joint.

[0054] The laser beam source can be configured as a solid-state laser, in particular a fiber laser, a disk laser, or a slab laser, or as a gas laser, in particular a CO2 laser. The laser beam source can be configured to generate a pulsed laser beam or a continuous-wave laser beam.

[0055] The beam deflection device can be designed as a scanner optic. The beam deflection device can include at least one scanner mirror over which the laser beam is guided. The scanner mirror can be positioned in different orientations or positions. For this purpose, the scanner mirror can have a piezoelectric or a galvo actuator. In other words, the scanner mirror can be designed as a piezoelectric or a galvo mirror. The scanner mirror can be positioned or oriented in such a way that the laser beam is directed through the openings for the purpose of creating the weld.

[0056] Alternatively, the beam deflection device can be designed as a small-field scanner or as a flying optic.

[0057] The beam deflection device can have an imaging ratio in a range of 1:1 to 5:1, in particular 1.5:1 to 2:1.

[0058] The laser welding device can include an optical fiber for guiding the laser beam. The optical fiber can be configured to split the laser beam into several individual beams. For example, the optical fiber can have a circular core and an annular core, the circular core and the annular core being arranged concentrically to each other. Advantageously, this can stabilize a vapor capillary (keyhole) that occurs during the welding process. A method according to the invention is designed for producing a weld joint of a stack of films using a laser beam. The method comprises the steps of: pressing a previously described welding mask onto the stack of films; generating the laser beam; and producing a weld joint by directing the laser beam through the openings.

[0059] The laser beam can be guided through the cutouts by passing it through each cutout sequentially. While being guided through one of the cutouts, the laser beam can follow a spiral, circular, or straight trajectory. For example, the laser beam can oscillate while being guided through one of the cutouts. This advantageously allows for the production of small, individual welds that enable tight pressure and the creation of crack-free or minimally cracked welds.

[0060] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show:

[0061] Fig. 1 shows a schematic representation of a laser welding device during the creation of a welded joint between a stack of foil and an electrical conductor using a laser beam.

[0062] Fig. 2 a schematic top view of a welding mask of the

[0063] Laser welding device of Fig. 1,

[0064] Fig. 3 shows a sectional view of the welding mask along a section line III-III according to Fig. 2.

[0065] Fig. 4 shows a sectional view of another embodiment of a

[0066] welding mask,

[0067] Fig. 5 is a schematic representation of the welding mask from Fig. 4 with a

[0068] Stacks of foil and an electrical conductor

[0069] Figs. 6 to 13 show various schematic representations of laser beam trajectories during the welding process; Fig. 14 shows a top view of another embodiment of a welding mask.

[0070] Fig. 15 shows a top view of another embodiment of a welding mask, and

[0071] Fig. 16 shows a schematic sequence of a process for producing a

[0072] Welded joint between a stack of foil and an electrical conductor.

[0073] Fig. 1 shows a laser welding device 10. The laser welding device 10 is designed as a laser welding machine. The laser welding device 10 is configured to produce a welded joint between a stack of foils 12 in the form of an electrode foil stack and an electrical conductor 14 in the form of a battery cell conductor by means of a laser beam 16.

[0074] The foil stack 12 is formed by a plurality of foils arranged one above the other, in particular stacked one on top of the other, in the form of electrode foils. In the illustrated embodiment, the foil stack 12 is formed by a total of 60 foils arranged one above the other. Each foil has a thickness of 10 pm. Each foil is made of an aluminum material of alloy group 1000.

[0075] The electrical conductor 14 and the foils of the foil stack 12 are made of the same material. In other words, the electrical conductor 14 is made of an aluminum alloy from group 1000. The electrical conductor 14 has a thickness of 0.4 mm.

[0076] When the foil stack 12 and the electrical conductor 14 are connected by means of the welding connection, the electrical conductor 14 and the foil stack 12 are suitable for the manufacture of a battery cell.

[0077] For the production of the battery cell, it is sufficient if the foil stack 12 and the electrical conductor 14 are only attached to each other by means of the welded connection. In other words, creating a further connection between the foil stack 12 and the electrical conductor 14 for the purpose of attaching the foil stack 12 to the electrical conductor 14 and / or for the purpose of electrically connecting the foil stack 12 to the electrical conductor 14 is not necessary.

[0078] The welded connection ensures that the foil stack 12 and the electrical conductor 14 are mechanically stable and electrically connected with low resistance. This makes the foil stack 12 and the electrical conductor 14 connected to the foil stack 12 by means of the welded connection particularly suitable for the production of the battery cell.

[0079] The laser welding device 10 has a laser beam source 18 for generating the laser beam 16. The laser beam source 18 is a solid-state laser in the form of a fiber laser. However, it is also conceivable that the laser beam source 18 is designed as a disk laser, a slab laser, or a gas laser, in particular a CO2 laser.

[0080] The laser beam 16 generated by the laser beam source 18 is a continuous-wave laser beam. The laser beam 16 is a single-mode laser beam with a Gaussian intensity profile and a diffraction coefficient M. 2 of less than 1.4. The laser beam 16 has a wavelength of 1064 nm and a power of 200 W (watts).

[0081] The laser welding device 10 has a beam deflection device 22 for directing the laser beam 16 onto the foil stack 12 for the purpose of producing the weld joint. The beam deflection device 22 can, for example, have an imaging ratio in the range of 1.6:1 to 1.9:1.

[0082] The beam deflection device 22 is designed as a scanner optic with at least one scanner mirror 24. The laser beam 16 is guided over the scanner mirror 24. The scanner mirror 24 has a galvo drive that can tilt a mirror surface of the scanner mirror 24 and thus move the scanner mirror 24 into different positions or orientations. By tilting the mirror surface, the laser beam 16 is directed at different points onto the stack of foils 12 by means of the beam deflection device 22.

[0083] The laser beam 16 is a focused laser beam. The laser beam 16 forms a laser spot, in particular a focus, on the foil stack 12. To form the focus on the foil stack 12, the laser welding device 10 can have a focusing lens (not shown in Fig. 1).

[0084] The laser beam 16 strikes the foil stack 12 with a beam parameter product of 0.6 mm*mrad. The beam diameter of the laser beam 16 on the foil stack 12 is 40 pm. However, it is also conceivable that the beam diameter of the laser beam 16 on the foil stack 12 has a value in the range of 30 pm to 170 pm. The laser welding device 10 has a welding mask 26. The welding mask 26 is shown in a schematic sectional view in Fig. 1. Figs. 2 and 3 show the welding mask in a larger view.

[0085] Fig. 2 shows that the welding mask 26 has a length 28 and a width 32. The length 28 is 60 mm and the width 32 is 30 mm. Fig. 3 shows that the welding mask 26 has a height 34. The height 34 is 10 mm.

[0086] Particularly as shown in Fig. 3, the welding mask 26 has a contact surface 36 for contacting the film stack 12. The contact surface 36 is a continuous, flat surface. To create the weld, the welding mask 26 is pressed, or in particular pressed, against the film stack 12, forming contact between the contact surface 36 and the film stack 12. By pressing the contact surface 36 against the film stack 12, gaps, in particular spaces, between the individual films of the film stack 12 are reduced. In other words, by pressing the contact surface 36 against the film stack 12, the individual films of the film stack 12 are pressed together. In particular, the individual films of the film stack 12 can be pressed together in such a way that the individual films touch each other.

[0087] The welding mask 26 has six cutouts 38. However, it is also conceivable that the welding mask 26 has more or fewer cutouts, in particular 4, 8 or 10 cutouts.

[0088] Each recess 38 extends from an inlet opening 42 of the welding mask 26 to an outlet opening 44 of the welding mask 26. Each recess 38 can extend along a longitudinal axis 46. Each longitudinal axis 46 of the recesses 38 can be straight. Each longitudinal axis 46 of the recesses 38 can be oriented orthogonally to the contact surface 36. Each recess 38 can have rotational symmetry with respect to its longitudinal axis 46.

[0089] The contact surface 36 and the outlet openings 44 are arranged on a first side 48 of the welding mask 26. The contact surface 36 borders each outlet opening 44. In other words, the contact surface 36 surrounds each outlet opening 44.

[0090] The inlet openings 42 are arranged on a second side 52 of the welding mask 26.

[0091] The first side 48 is opposite to the second side 52. Each entrance opening 42 is circular with a diameter 54 of 5 mm. Thus, each entrance opening 42 has an area of ​​20 mm². 2 Each outlet opening 44 is circular with a diameter 56 of 4 mm. Therefore, each outlet opening 44 has an area of ​​13 mm². 2 This means that the area of ​​each inlet opening 42 is at least 40% larger than the area of ​​each outlet opening 44.

[0092] Fig. 2 shows that a center point 62 of each inlet opening 42 and a center point 64 of each outlet opening 44 are arranged on the longitudinal axis 46 of the respective recess 38. Thus, the center point 62 of the inlet opening 42 is connected to the center point 64 of the outlet opening 44 via the longitudinal axis 46 of the outlet opening 44, which extends from the inlet opening 42 to the outlet opening 44.

[0093] Each center point 62 of the inlet openings 42 is a geometric centroid in the form of a centroid of the respective inlet opening 42. Each center point 64 of the outlet openings 44 is a geometric centroid in the form of a centroid of the respective outlet opening 44.

[0094] A distance 66 between two adjacent inlet openings 42, in particular between the centers 62 of two adjacent inlet openings 42, in the longitudinal direction of the welding mask 26, is less than 5 times the diameter 54 of one of the two adjacent inlet openings 42. The distance 66 is 10 mm. A distance 68 between two adjacent inlet openings 42, in particular between the centers 62 of two adjacent inlet openings 42, in the transverse direction of the welding mask 26, is less than 5 times the diameter 54 of one of the two adjacent inlet openings 42. The distance 68 is 8 mm.

[0095] The distance between two adjacent outlet openings 44, in particular between the centers 64 of two adjacent outlet openings 44, in the longitudinal direction of the welding mask 26, is less than 5 times the diameter 56 of one of the two adjacent outlet openings 44. The distance between the two adjacent outlet openings 44 in the longitudinal direction is equal to the distance 66 between the two adjacent inlet openings 42.

[0096] The distance between two adjacent outlet openings 44, in particular between the centers 64 of two adjacent outlet openings 44, in the transverse direction of the welding mask 26, is less than 5 times the diameter 54 of one of the two adjacent outlet openings 44. The distance between the two adjacent outlet openings 44 in the transverse direction is equal to the distance 68 between the two adjacent inlet openings 42.

[0097] Each recess 38 extends from the inlet opening 42 to the outlet opening 44 such that the cross-sectional area of ​​the recess 38 decreases from the inlet opening 42 to the outlet opening 44. Figure 3, in particular, shows that each recess 38 has a frustoconical section that transitions into a cylindrical section of the recess 38. Due to the frustoconical section, each recess 38 is conically shaped in sections.

[0098] Fig. 1 shows that the welding mask 26 is pressed onto the stack of foils 12. Each exit opening 44 on the stack of foils 12 defines a welding area. The laser beam 16 can strike the stack of foils 12 within this welding area. The laser beam 16 is guided across the stack of foils 12, particularly the welding area, thereby creating a weld point of the weld joint. All weld points created constitute the weld joint. The number of weld points is equal to the number of exit openings 44.

[0099] Fig. 1 shows the laser beam 16 during the creation of a weld. The laser beam 16 is guided through a recess 38 before it hits the stack of foil 12.

[0100] Each recess 38 forms a passage for the laser beam 16 to pass through the welding mask 26. In other words, the recesses 38 are designed so that the laser beam 16 is directed through them. For this purpose, the scanner mirror 24 is positioned in different orientations or configurations such that the laser beam 16 is directed through the recesses 38 to create the weld.

[0101] Figures 4 and 5 show a further embodiment of the welding mask 26 from Figures 1 to 3, where the same reference numerals are used for identical and functionally equivalent elements. Reference can therefore be made to the above descriptions of the embodiment in Figures 1 to 3, so that essentially only the existing differences are discussed. Figure 4 shows that each outlet opening 44 is bounded by a projection 72 of the welding mask 26. The welding mask 26 has a total of six projections 72. Each projection 72 forms a section of the contact surface 36. The contact surface 36 can only be formed by the projections 72. Each projection has a height 74 of 0.6 mm. However, a height 74 in the range of 0.5 mm to 10 mm is also conceivable.

[0102] Fig. 5 shows that the welding mask 26 only contacts the foil stack 12 with its contact surface 36 to create the weld joint.

[0103] Figures 6 to 12 show different representations of how the laser beam 16 can be directed over the welding area to produce a single weld point, using the same reference numerals for identical and functionally equivalent elements, so that essentially only the essential differences are discussed.

[0104] In Figs. 6 to 12, the outlet opening 44 is shown with a dashed line.

[0105] Fig. 6 shows a beam cross-section 76 of the laser beam 16, which strikes the foil stack 12 for the production of a single weld point of the weld joint without any movement.

[0106] Fig. 7 shows a trajectory 78 along which the laser beam 16 is guided over the foil stack 12 during the creation of a single weld point of the weld joint. The trajectory 78 is straight. The laser beam 16 is moved back and forth along the straight trajectory 78.

[0107] Fig. 8 shows an alternative path for the trajectory 78. In Fig. 8, the trajectory 78 is spiral. The laser beam 16 is guided spirally over the stack of foils 12 during the creation of a single weld point of the weld joint.

[0108] Fig. 9 shows another alternative path of the trajectory 78. In Fig. 9, the trajectory 78 is circular. The laser beam 16 is guided circularly over the stack of foils 12 during the creation of a single weld point of the weld joint.

[0109] Fig. 10 shows another alternative path of trajectory 78. In Fig. 10, trajectory 78 has a first trajectory segment 80 and a second trajectory segment 82. Both trajectory segments 80 and 82 are circular. Both trajectory segments 80 and 82 are arranged concentrically to each other. Fig. 11 shows another alternative path of trajectory 78. In Fig. 11, trajectory 78 has a first trajectory segment 80, a second trajectory segment 82, a third trajectory segment 84, and a fourth trajectory segment 86. The four trajectory segments 80, 82, 84, and 86 are circular. The four trajectory sections 80, 82, 84, 86 are arranged in such a way that the individual trajectory sections 80, 82, 84, 86 overlap with each other.

[0110] Fig. 12 shows another alternative course of trajectory 78. In Fig. 12, trajectory 78 has several trajectory segments that are straight and parallel to each other.

[0111] Fig. 13 shows a further embodiment of the laser beam 16 from Figs. 1 to 12, wherein identical and functionally equivalent elements use the same reference numerals and in this respect reference can be made to the above explanations of the embodiments of Figs. 1 to 12, so that essentially only the existing differences are discussed.

[0112] In Fig. 13, the outlet opening 44 is shown with a dashed line.

[0113] The laser beam 16 is a laser beam bundle. The laser beam 16 is formed from four individual beams 88. As a result, the laser beam 16 forms four foci on the foil stack 12. During the welding process, the beams 88 are moved along a circular trajectory 90.

[0114] Figures 14 and 15 each show a further embodiment of the welding mask 26 from Figures 1 to 3, whereby the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the above explanations of the embodiment of Figures 1 to 3, so that essentially only the existing differences are discussed.

[0115] Fig. 14 shows the welding mask 26 with four recesses 38, four inlet openings 42 and four outlet openings 44. Each inlet opening 42 and each outlet opening 44 is elliptical. Each recess 38 has an elliptical cross-section.

[0116] The longitudinal distance 66 between two adjacent entrance openings 42 is less than 5 times the length of a principal axis of either of the two elliptical entrance openings 42. The transverse distance 68 between two adjacent entrance openings 42 is less than 5 times the length of a minor axis of either of the two elliptical entrance openings 42.

[0117] Fig. 15 shows the welding mask 26 with four recesses 38, four inlet openings 42, and four outlet openings 44. Each inlet opening 42 and each outlet opening 44 is rectangular. Each recess 38 has a rectangular cross-section.

[0118] The distance 66 between two adjacent entrance openings 42 in the longitudinal direction is less than 5 times the length of the two elliptical entrance openings 42.

[0119] The distance 68 between two adjacent entrance openings 42 in the transverse direction is less than 5 times the width of the two elliptical entrance openings 42.

[0120] Fig. 16 shows an exemplary sequence of a method for producing a welded joint of a stack of foils using a laser beam. The laser welding device 10 of Fig. 1 is configured to carry out the method.

[0121] The process comprises the following steps: a) pressing a previously described welding mask 26 onto the foil stack 12; b) generating the laser beam 16; and c) producing a

[0122] Welding joint by directing the laser beam 16 through the recesses 38.

Claims

Patent claims 1. Welding mask (26) for a laser welding device (10) for producing a welded joint between a stack of foils (12) and an electrical conductor (14) by means of a laser beam (16), comprising: a contact surface (36) for contacting the stack of foils (12), and a plurality of recesses (38) for directing the laser beam (16) onto the stack of foils (12) through the recesses (38) for the purpose of producing the welded joint, wherein each recess (38) extends from an inlet opening (42) to an outlet opening (44), wherein a distance (66, 68) between two adjacent inlet openings (42) is less than 5 times, in particular 3 times, 2 times or 1.5 times, a diameter of one of the two adjacent inlet openings (42), and / or wherein a distance (66, 68) between two adjacent outlet openings (44) is less than 5 times, in particular 3 times, 2 times or 1.5 times,a diameter of one of the two adjacent outlet openings (44)., 2. Welding mask (26) according to claim 1, wherein each outlet opening (44) is adjacent to the contact surface (36).

3. Welding mask (26) according to one of the preceding claims, wherein each outlet opening (44) has an area of ​​less than 150 mm² 2 exhibits.

4. Welding mask (26) according to one of the preceding claims, wherein each inlet opening (42) has an area whose value is at least 10% greater than an area of ​​the outlet opening (44).

5. Welding mask (26) according to one of the preceding claims, wherein a cross-sectional area of ​​each recess (38) decreases from the inlet opening (42) to the outlet opening (44).

6. Welding mask (26) according to one of the preceding claims, wherein each inlet opening (42) and / or each outlet opening (44) is circular, oval or rectangular in shape.

7. Welding mask (26) according to one of the preceding claims, wherein the welding mask (26) has a plurality of projections (72), each projection (72) defining an outlet opening (44) and forming a section of the contact surface (36).

8. Welding mask (26) according to claim 7, wherein each projection (72) has a height of at least 0.5 mm.

9. Laser welding device (10), in particular laser welding machine, for producing a welded joint between a stack of foils (12) and an electrical conductor (14) by means of a laser beam (16), comprising: a laser beam source (18) for generating the laser beam (16), a beam deflection device (22) for directing the laser beam (16) onto the stack of foils (12), and a welding mask (26) according to one of the preceding claims, wherein the beam deflection device (22) is configured to direct the laser beam (16) through the openings (38) for the purpose of producing the welded joint.

10. Method for producing a welded joint between a stack of foil (12) and an electrical conductor (14) using a laser beam (16), the method comprising the steps: Pressing a welding mask (26) according to one of the preceding claims 1 to 8 onto the stack of foil (12), Generating the laser beam (16), and Creating a weld joint by directing the laser beam (16) through the recesses (38).

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