WO2021074427A1

WO2021074427A1 - Method for joining two joining partners by means of ultra-short laser pulses

Info

Publication number: WO2021074427A1
Application number: PCT/EP2020/079279
Authority: WO
Inventors: Felix Zimmermann
Original assignee: Trumpf Laser- Und Systemtechnik Gmbh
Priority date: 2019-10-18
Filing date: 2020-10-16
Publication date: 2021-04-22
Also published as: DE102019128251A1

Abstract

The invention relates to a method for joining two joining partners (3) by means of ultra-short laser pulses of a joining beam, preferably for joining at least one joining partner that is substantially transparent to the laser pulses to a further joining partner, particularly preferably for joining two joining partners that are transparent to the laser pulses, wherein a joining beam (1) comprising ultra-short laser pulses is introduced into the joining partners (5) to locally melt a joining region (11). In this way, a processing region (21) is heated with at least one processing beam (2), wherein the joining beam (1) and the processing beam (2) are positioned next to one another such that the joining region (11) and the processing region (21) do not physically overlap and/or wherein the joining beam (1) and the processing beam (2) are designed such that the laser pulses of the processing beam (2) and the joining beam (1) do not temporally overlap.

Description

Method for joining two joining partners using ultra-short laser pulses

Technical area

The invention relates to a method for joining two joining partners by means of ultrashort laser pulses, preferably for joining at least one joining partner that is essentially transparent for the laser pulses with another joining partner, particularly preferably for joining two joining partners that are transparent for the laser pulses and in particular for joining two glasses by means of ultrashort laser pulses.

State of the art

To join two parts to be joined together, it is known to apply a laser beam to the respective part to be joined in order to generate a melt in the zone acted upon by the laser beam through energy absorption, which forms a weld seam between the parts to be joined after the melt has solidified.

In this context, it is particularly known to place the focus of the laser beam between the two parts to be joined in order to produce a weld between a transparent joint partner and a non-transparent joint partner or in order to weld two transparent joint partners. This is achieved by focusing the processing laser beam in such a way that the energy input is highest in the interface between the joining partners in order to provide a melt between the two joining partners and then a weld seam after solidification. The processing laser beam passes through one of the transparent joining partners and is only focused on the side of the joining partner opposite the entry area.

The processing laser beam is focused by appropriate optics and the associated beam shaping into the material of one of the joining partners, into both joining partners and / or into the area of an interface between the two mutually adjacent joining partners. When joining parts to be joined, the strong local energy input from the focused laser beam results in high temperatures that are not present in the surrounding material areas. Correspondingly, the heat required for processing - for example for the production of a weld seam - leads to temperature stresses in relation to the surrounding material areas. Correspondingly, there can be tensions and / or cracks in the material in the area of the weld seam, which can result in a reduction in the quality of the joined materials.

If ultrashort laser pulses are focused in the volume of glass, e.g. quartz glass, the high intensity in the focus leads to non-linear absorption processes. Depending on the laser parameters, various material modifications can be made to the glass. If the time interval between the successive ultrashort laser pulses is shorter than the heat diffusion time, this leads to heat accumulation or a temperature rise in the glass in the focus area. With each of the successive pulses, the temperature can then be increased to the melting temperature of the glass and finally the glass can be locally melted.

Through the transparent joining partners, for example the glasses to be joined together, it can be achieved that the laser focus can be focused through the glass body aligned in the beam direction onto the interface between the joining partners. Due to the successive heat accumulation from pulse to pulse, the absorption zone shifts longitudinally in the direction of the laser incidence direction, so that finally the melt from the glass enters the interface. When the melt cools down, a stable connection between the two glasses can then be created, with the weld seam appearing elongated in the direction of laser incidence as a result of the previous process. In the case of a small gap between the parts to be joined, it is possible that the melt bridges the gap so that glasses with smaller unevenness that are not completely flat against one another can also be joined.

In US Pat. No. 8,314,359 B2 and US Pat. No. 9,625,713 B2, systems and methods are described in which two optically transparent materials are melted locally in the area of the common interface by means of ultrashort laser pulses and are thereby finally welded together. US2015 / 273624A1 describes a method in which two spatially and temporally superimposed laser pulses are combined in order to exceed the threshold intensity for a joining process. US2016 / 0318122A1 describes a method for increased material processing described, in which the life of a plasma state initiated by an ultrashort laser pulse is extended with the timely introduction of a long laser pulse.

In these processes, however, the high temperature gradients that occur from the welding point to the environment in the glass can cause material stresses that can result in cracking.

Presentation of the invention

Based on the known joining methods, it is an object of the present invention to specify a joining method which reduces or prevents the formation of cracks.

Accordingly, a method for joining joining partners by means of ultrashort laser pulses of a joining beam is specified, preferably for joining at least one material that is essentially transparent for the laser pulses with a further joining partner, particularly preferably for joining two materials that are transparent for the laser pulses, with one ultrashort laser pulses being more comprehensive Joining beam for local melting of a joining area is introduced into the joint partner. According to the invention, a process area is heated with at least one process beam, the joining beam and the process beam being placed next to one another in such a way that the joining area and the process area do not spatially overlap and / or the joining beam and the process beam are designed so that the laser pulses of the process beam and of the joining beam do not overlap in time.

In this way, a joining environment can be heated spatially around the joining area and / or before and / or after the joining process by means of the process beam.

The joining partners to be joined are in contact with one another at an interface. The melting of the material of the joining partners in the joining area takes place, among other things, at the interface, so that the resulting melt bridges the interface and a joint is established at the interface after the melt has solidified.

The method is preferably applied to two joining partners made of glass, for example quartz glass, in which the joining beam of an ultrashort pulse laser is focused through the upper joining partner, which is transparent for the wavelength of the ultrashort pulse laser, into the vicinity or exactly on the common interface of the two joining partners. The method can also be used to join a first joining partner that is transparent to the joining beam and a second joining partner that is essentially opaque to the joining beam, for example for joining a first joining partner made of glass with a second joining partner made of metal, for example aluminum. The joining beam enters through the joining partner that is transparent to the joining beam.

In the joining area, the successive absorption of the laser pulses causes heat to accumulate, provided that the pulse rate of the joining beam is greater than the rate of heat dissipation through material-specific heat transport mechanisms. Due to the increasing temperature from pulse to pulse, the melting temperature of the joining partner can finally be reached, which leads to a local melting of the material of the first joining partner into which the joining beam enters. The resulting melt can bridge the common interface and permanently connect the parts to be joined together when it cools.

The size of the joining area is determined by the beam geometry, in particular the focus diameter of the joining beam.

A joining environment is defined here as the area that heats up as a whole as a result of the absorption of the joining beam and the subsequent heat transport. The size and extent of the joining environment is determined by the heat diffusion time and the laser absorption capacity of the glass as well as the joining pulse rate. The joining area can, for example, be twenty times the diameter of the joining area, or six to ten times the size of the joining area. For example, thermal gradients of a 50 μm wide weld seam can also show up to 400 μm outside the weld seam.

Due to the large temperature gradients that arise in the area around the joint, material stresses can occur, which promote the formation of cracks. In order to avoid crack formation spatially in the joining area due to excessive or too rapid heating or cooling and excessive temperature gradients, the joining area is additionally heated by the process beam in the process area.

The process area is determined analogously to the joining area via the beam geometry, in particular via the focus diameter of the process beam. A process environment is defined here as the area that heats up overall as a result of the absorption of the process beam and the subsequent heat transport. The size and extent of the process environment is included determined by the heat diffusion time and the laser absorption capacity of the joint partner, and thus by the average coupled process performance. Analogous to the joining environment, the process environment can, for example, be twenty times the diameter of the process area, or also ten times the size of the process area.

The joining environment and the process environment preferably overlap at least partially, so that, for example, the higher temperature in the process environment can reduce material stresses in the joining environment. The overlap of the joining and process environment is given by the distance between the joining and process areas, the heat diffusion time of the glass and the corresponding laser absorption capacity for the joining and process laser light, and the average coupled power of the joining and process lasers.

The joining environment can thus be heated spatially around the joining area with a process laser if the process environment and the joining environment overlap.

The process beam can comprise ultrashort laser pulses or continuous wave radiation.

The process area can be heated before and / or after the joining process.

Time before the joining process means that the pulse of the joining beam hits an already heated joining area or hits the process environment. Temporally after the joining process means that the process beam hits the joining area, or the overlap between the process area and the joining area is formed after the joining beam hits. The time interval between the joining beam and the process beam should preferably be selected to be smaller than the typical heat diffusion time in the glass, for example smaller than 10 ps.

Of course, the process area can also be heated at the same time as the joining process.

It is also possible for the process beam and the joining beam to be generated by one and the same ultrashort pulse laser and, for example, to be split into two beams of different intensity by beam splitter optics. A temporal offset of the pulses of the process beam and the joining beam can then be implemented through different beam paths and the associated different transit times of the partial beams to the joint partner.

The ultrashort pulse laser that generates the joining beam is referred to herein as the joining fiber. The laser that generates the at least one process beam is referred to herein as a process laser. It is possible here for the process laser to be a continuous wave laser and the joining fiber to be an ultra-short pulse laser. In particular, the process laser and the joining fiber can also perform the other task mutatis mutandis.

If only one laser is used, the terms process and joining fibers can be used synonymously - the joining beam and the process beam are nevertheless designed as separate beams.

In particular, the process laser can fulfill various functions regardless of the precise operating mode. For example, it can act thermally on material modifications or act on the surrounding areas of the material modification. The process laser can also be used to produce tailor-made permanent material modifications, for example to heal stresses in the material, to reshape material or to expand previously produced weld seams.

One advantage of this method is that material stresses from the joining environment are healed or reduced by the process beam, so that crack formation is suppressed.

This also makes it possible to join materials permanently and with high strength, even with low sample evenness or large gap distances. In addition, no additional materials such as adhesives are used in this process, which means that costs can be reduced. In addition, the throughput of parts to be joined can be increased by eliminating the drying process.

In a further embodiment, the joining beam and the at least one process beam are not generated by the same laser.

In particular, different lasers can be used as a result, so that optimal laser parameters can be set independently of one another for the joining beam and the at least one process beam. For example, the joining pulse rate and the pulse repetition rate can be selected differently. Since the material of the joining partner should not be melted with the process beam, a lower average process output, for example through a lower pulse repetition rate with the same laser pulse intensity, can be selected as with the joining beam. However, it is also possible for the process beam to have a different wavelength than the joining beam, or for the fluence of the process beam to be smaller than that of the joining beam due to a different focus. The intensity in the joining spot introduced into the material by the joining fiber is preferably ten times greater than the intensity introduced into the material by the process laser in the heating spot. However, the process beam can also have the same or lower intensity than the main beam.

The at least one process beam preferably has a central spot and at least one further process area.

A central spot means that there is a local maximum in the beam's intensity profile in the center of the beam. A further process area is understood here to mean that a further area with a non-vanishing laser intensity follows radially from the central spot. In particular, the central spot can also be used to join the glasses, with the further process area of low intensity only being used to heat the joining environment.

By choosing a suitable beam geometry, the intensity profile of the process laser can be impressed on the process environment of the process area, which in particular enables particularly advantageous thermal gradients to be implemented in the joining partners.

The profile of the central spot of the at least one process beam and / or the at least one further process area of the at least one process beam can be Gauss-shaped, or Bessel-shaped or Laguerre-Gauss-shaped, or as a superposition of the aforementioned.

As a result, it can be achieved that Gaussian, Bessel or Laguerre-Gaussian intensity profiles correspond to the natural laser modes of a laser and so the method can be used without additional optical adjustment effort.

The at least one further process area of the at least one process beam can comprise at least one higher order of diffraction.

In this way it can be achieved that the heating profile of the process beam can be determined directly by a suitable choice of a higher diffraction order. It is thus possible to use diffraction orders that enable the most extensive possible illumination with the process beam.

The central spot and the at least one further process area of the at least one process beam can be offset longitudinally with respect to one another. In this context, offset longitudinally means that the central spot and the process area are offset from one another in the direction of the beam. In particular, it is hereby possible that what is known as spatial mode beating of the laser modes can be used constructively, so that several intensity maxima can result in the beam direction of the at least one process beam. However, the process area and the central spot can also be offset from one another by means of suitable optics. This is particularly the case when several laser beams are superimposed to implement the process beam.

This means that the process beam can also create a longitudinal heat profile in the glasses, since the stresses during the joining process not only fade out transversely along the interface, but can also protrude into the glass. In this way, material stresses in the glass can also be effectively reduced.

The beam shape of the at least one process beam can be generated by means of a beam-shaping unit and / or by means of a spatial light modulator and / or by means of a diffractive element and / or by means of an acousto-optical deflector.

A beam-shaping unit can in particular be an objective for focusing the laser beam. A spatial light modulator enables the process beam to be fanned out to a given geometry, for example round, square or star-shaped. A diffractive element also allows the process beam to be fanned out to a given geometry.

An acousto-optical deflector makes it possible to deflect the process beam periodically in time, so that in particular Lissajous-figure-shaped heating patterns can be generated in the interface so that a larger area is heated. The deflection by means of acousto-optical deflector also allows a randomized movement pattern, so-called random access scanning, which enables the rapid scanning of any heating pattern.

This means that special geometries can be created with simple means that are heated by the process beam so that, for example, joints that are exposed to particular stresses - for example on edges or tips - experience a specially adapted material relaxation.

The at least one process beam can be moved around the joining beam. Moved around the joining beam means in this context that the process beam moves relative to the joining beam in a temporally variable manner. In particular, this embodiment provides that the joining beam is the center of a movement of the process beam, such as, for example, the center of symmetry in the case of a radial movement or a pendulum movement. In particular, a movement of the process beam around the joining beam comprises a movement along (longitudinal) or perpendicular (laterally) to the direction of movement of the joining beam.

It can thereby be achieved that simple geometric shapes can be heated and parameterized relative to the joining beam. For example, with an additionally moving joining beam, it is possible to generate complex heated geometries of the process laser.

The movement of the at least one process beam can be circular or figure-eight, or the trajectory of the movement can consist of two touching circles or similar geometries.

It can thereby be achieved that the joining beam can be placed in the center of symmetry, so that the glasses can be tempered symmetrically and evenly around the joining area.

In this way it can also be achieved that so-called wobble figures are created when an additionally moving joining beam is used, which in this context enables a particularly stable and tension-free connection between the two glasses.

In the case of a movement of the joining beam, the at least one process beam can precede or follow the joining beam, or run parallel and with a lateral offset to the joining beam.

A process beam following the joining beam can adjust any material defects such as tensions or cracks to the surroundings due to the heating of the material during the joining process. For example, cracks in one or both of the joining partners caused by the joining process can also be compensated for by the fact that the respective material flows into the crack and thus closes it.

In this embodiment, the process beam runs in front of the joining beam when it is in front of it in the process direction of the joining beam. Analogously to this, the process beam follows the joining beam if the process beam is located behind the joining beam in the process direction of the joining beam. The at least one process beam has a lateral offset when it does not coincide with the joining beam. The movement of the at least one process beam runs parallel to the joining beam if it takes place at the same speed and in the same direction.

It can thereby be achieved that the joining beam can join the joining partners in the already relaxed state. On the other hand, the method can also simultaneously enable slower cooling by the subsequent process beam. In the event that there is only one process beam and one joining beam, the beams can have the same beam intensity.

For this purpose, for example, the ultrashort pulse laser beam can be split into two equally intense beam parts with a 50-50 beam splitter.

It can thereby be achieved that the adjustment effort for the optical system is reduced by the simple optical structure and a simple power adjustment is given by the same source for joining and process beam.

The joining beam can also be preceded by two process beams and two process beams can follow it.

Two leading and trailing process beams have the advantage that the temperature can be controlled over a larger area.

A particularly advantageous embodiment of the method provides that the process beams are arranged symmetrically around the joining beam.

In this case, symmetrical around the joining beam means that the process beams lie, for example, on a common round or square geometry, in whose center of symmetry the joining beam is located.

As before, it can be achieved that in the case of a heat diffusion running symmetrically to the joining area, the material stresses are reduced symmetrically to the joining center by the process beams.

The process beams can preferably each have approximately one tenth the intensity of the joining beam. The movement of the at least one process beam can be generated by means of an acousto-optical deflector and / or a scanner unit and / or a micro-scanner.

These optical and easily accessible means make it possible to control the process and joining beam alignment with the aid of a computer, for example. The process beam is preferably designed in such a way that it does not melt the process area. In other words, only the joining beam is designed to melt the material of the joining partners, whereas the at least one process beam only leads to heating of the process area, which does not lead to melting of the material in the process area.

Brief description of the figures

Preferred further embodiments of the invention are explained in more detail by the following description of the figures. Show:

FIGS. 1A, B show a schematic representation of a joining and process area;

FIG. 2 shows a time profile of the ultra-short process and joining pulses; FIGS. 3A, B show a schematic representation of the process areas;

FIG. 4 shows a longitudinal offset of the further process areas and the central spot;

FIG. 5 shows a sketch of a general trajectory of the process beam around the joining beam;

6A, B, C circular, figure-eight and linear trajectories of the process beam around the joining beam; FIG. 7A, B trajectories of a process beam when moving around the moving joining beam;

FIG. 8 a sketch of possible trajectories of four process beams around the moving one

Joining beam around; and

FIG. 9 shows a sketch of process beams placed symmetrically around the joining beam.

Detailed description of preferred exemplary embodiments Preferred exemplary embodiments are described below with reference to the figures. Identical, similar or identically acting elements are provided with identical reference symbols in the different figures, and a repeated description of these elements is in some cases dispensed with in order to avoid redundancies.

FIG. 1, comprising FIG. 1 A and FIG. 1 B, shows two joining partners 3 to be joined, which rest against one another at an interface 5. The two joining partners 3 can be, for example, two glasses which are in contact with one another at the interface 5 and which are to be joined to one another at this interface 5.

In the method shown as an example in FIG. 1, a process beam 2 is placed laterally next to a joining beam 1. Both beams are focused in the interface 5 between the two joining partners 3, which is represented by the minimal beam waist.

The foci can, however, also be located under the interface of the materials to be joined.

The foci can, however, also fall apart and, for example, the focus of the joining beam 1 can be arranged below the interface 5 between the two joining partners 3 and the focus of the process beam 2 can then, for example, be placed in the interface 5 between the two joining partners 3.

In order to achieve a stable connection via the interface 5, the joining partners 3 are melted locally in the joining area 11. This is achieved in that the joining beam 1 comprises a number, for example ten, successive laser pulses which are successively absorbed by the joining partner 3 in the joining area 11. As a result of non-linear absorption processes, this leads to heat accumulation in the joining partner 3, provided that the time interval between the pulses is shorter than the heat diffusion time of the joining partner 3. Thus, after absorption of the laser pulses, the melting temperature can be exceeded and the joining partner 3 is locally melted. In particular, it should be pointed out here that by cleverly positioning the laser focus it can be achieved that both joining partners can be melted at the same time. When the melt passes over the interface 5 and cools, it can lead to a stable connection between the two joining partners 3.

After each absorbed joining pulse, the heat rises in the joining area 11 in the joining partner 3.

However, this heat is also given off into the joining environment 12 by heat diffusion in accordance with the heat diffusion time. This creates a joining temperature gradient from the joining area 11 to the edge of the joining area 12. The joining temperature gradient depends on the difference between the melting temperature and the temperature of the joining partners outside the joining area. If this joining temperature gradient is too high, stresses can arise in the material 6, which ultimately lead to crack formation.

In order to prevent the formation of cracks, the joining temperature gradient must therefore be reduced, but the temperature in the joining area always at least corresponds to the melting temperature of the joining partner. This can be done by heating the joining area to a higher temperature, or by artificially increasing the joining area so that the temperature difference is formed in the joining partner over a longer distance.

Both effects can be exploited by the present method. For this purpose, a process beam 2 is placed next to the joining beam 1. The process beam 2 heats the process area 21. In contrast to the joining beam 1, however, no joining partner 3 should be melted with the process beam 2. The average power of the process laser or the process beam 2 is, however, also absorbed in the process area 21 of the joining partner 3, so that there is a rise in temperature there. The heat flows away from the process area 21 by heat diffusion, so that a process environment 22 is formed. A heating temperature gradient that is smaller than the joining temperature gradient is thus also formed from the process area 21 to the edge of the process environment 22. In particular, the temperature in the entire process environment 22 is increased or at least equal to the temperature of the joining partner 3 outside the joining environment 12 and the process environment 22.

If the process area 21 and the joining area 11 are placed close enough to one another, the formed process environment 22 and joining environment 12 overlap. This ensures that the joint partner 3 has a higher temperature in the area of the overlap 4 than if no process environment 22 were formed . The joining area 12 in particular now has an increased temperature in the area of the overlap 4, so that the joining temperature gradient from the joining area 11 to the edge of the joining area 12 in the area of the overlap 4 has been artificially reduced. Due to the lower joining temperature gradient, material stress 6 can thus be reduced. At the same time, the joining partner 3 has an entire temperature gradient, which now extends from the joining area 11 to the edge of the process area 21, so that the temperature decrease takes place over a larger area on average.

In particular, the roles of the joining and process lasers can be reversed mutatis mutandis. Furthermore, in one embodiment, the process beam 2 can also at least partially melt the process area 21 and thus expand the area melted in the joining environment 11 or expand a central modification.

In FIG. 1A it is shown that in the joining area 11 or in the process area 21, the intensities of the joining or process beams are greatest. In contrast to process beam 2, however, the joining beam 1 is intense enough to melt the joining partner 3 near the interface 5, so that with successive ultrashort pulse absorption the melt center moves towards the interface 5, the melt exits there and via the interface 5 to the opposite joining partner 3 propagated, with which the melt then forms a firm bond when it cools.

In one embodiment of the method, the processing and joining fibers used have a tunable wavelength in the range from 200 nm to 5000 nm. Because of the wavelength range that goes beyond the optically visible range, in a further embodiment everything is considered to be glass that is transparent for the selected laser wavelength. The repetition rates are between continuous wave irradiation, 100Hz and 50MHz. Bursts are also conceivable, the repetition rate of the pulses in the burst being between 1 MHz and 50 GHz. The laser pulses are between 10fs and 50ps long. The laser beams are also focused in such a way that a fluence in the focus zone of more than 10 mJ / cm ² can be achieved. The modification threshold of the joining partners is typically between 1 J / cm ² and 5 ^{J / cm 2} . In order to increase the strength of the weld, for example, the pulse energies can also be modulated over time.

In FIG. 1 B, the joining environment 12 and the process environment 22 are shown in a top view. As a result of the heat transport from the process area 21 or the joining area 11, the process environment 22 and the joining environment 12 are formed so that they overlap in the overlap 4. In the overlap 4, the joining area 12 experiences a temperature increase. If material tension should have arisen or arise in the overlap 4 because of the strong temperature gradient around the joining area 11, then this can be reduced by the additional heating process so that there is no crack or crack in the joining partner.

FIG. 2 shows that the joining beam 1 and the process beam 2 can strike at different times for one location. In particular, it is shown that the intensity I of a process pulse can be different from the intensity of the joining pulse. In particular, it is also shown that the process beam can hit the joining partner both after the joining pulse (the abscissa axis points in the positive direction) and before the joining pulse (the abscissa axis points in the negative direction).

FIG. 3A shows how a central spot 23 and a further process area 24 are combined to form the actual process area 21 through a corresponding design of the process beam 2. The intensity profile shown below shows that the central spot 23 and the further process area 24 can be composed of different beam profiles. The intensity distribution of the central spot 23 is thus distributed over a significantly smaller area than that of the further process area 24.

FIG. 3B shows that the further process area 24 can also consist of a higher mode, in particular of Gauss, Bessel and / or Laguerre-Gauss modes.

FIG. 4 shows a process beam 2 which is focused in the first joining partner 3 in such a way that the central spot 23 of the process beam 2 lies at the interface 5 of the first joining partner in the direction of the beam. The joining area 11 of the joining beam 1 (not shown) can coincide with the central spot 23. The further process areas 24 are located longitudinally offset in relation to this in the joining partner 3 and not on the surface. As a result, material stresses 6 which run from the interface 5 into the joining partner 3 are reduced.

FIG. 5 shows an embodiment of the method in which the process beam 2 is moved around the joining beam 1. The joining beam 1 is located at the origin of the coordinate system in order to make it clear that any symmetries of the process beam trajectory relate to the current location of the joining beam 1. In particular, the time arrow is shown in such a way that it points to both positive and negative times. This is intended to symbolize at this point that the direction of the movement can be freely selected, so that, for example, clockwise or counterclockwise movements are possible.

In FIG. 6, comprising FIGS. 6A, 6B and 6C, various possible movements of the process beam 2 are shown, namely circular 6A, figure-of-eight 6B and linear 6C. In all the variants shown here, the process beam 2 moves relative to the joining beam 1. The different shapes can be produced, for example, with an acousto-optic deflector. When the process beam passes through an acousto-optic deflector, it is periodically deflected, for example in the x and y directions. By choosing the frequency of the x-deflection and y-deflection and superimposing the periodic deflections in the correct phase, 2 Lissajous figures can be generated with the process beam. In FIG. 7A, an embodiment of the method is shown in which the joining beam 1 is moved with a feed along the x-axis. The feed is, for example, of the order of magnitude between 10 pm / s and 1 m / s. At the same time, the process beam 2 is moved in a circle around the joining beam 1. A so-called wobble figure results from the process beam trajectory, by means of which a uniform temperature control of the joining environment 12 is made possible. Analogously to this, FIG. 7B shows an embodiment in which the process beam moves linearly up and down relative to the joining beam along the y-axis. This results in a sawtooth curve of the process beam trajectory. It should also be pointed out that in the embodiment shown, the process beam 2 follows the joining beam 1.

FIG. 8 shows an embodiment in which two process beams 2 each precede the joining beam 1 and two process beams 2 each follow. The process beams 2 move on trajectories around the joining beam 1, which originate from a figure-eight movement.

A further embodiment is shown in FIG. 9, in which two process beams 2 each lead in front of the joining beam 1 and two process beams 2 each follow the joining beam 1. The process beams 2 are placed symmetrically around the joining beam 1, so that a symmetrical temperature gradient around the joining area 11 can be implemented. Furthermore, the process beams 2 have a lower intensity than the joining beam, for example 10% each of the joining beam intensity, which is characterized by the smaller diameter of the process beams in the figure.

The process beams 2 that follow the joining beam 1 can adjust any material defects, such as tension or cracks, to the surroundings due to the heating of the material following the actual joining process during the joining process. For example, cracks in one or both of the joining partners caused by the joining process can also be compensated for by the fact that the respective material flows into the crack and thus closes it.

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

I joining beam

I I joining area 12 joining environment 2 process beam

21 Process area

22 Process environment

23 central spot

24 further process area 3 joining partners

4 overlap

5 interface

6 material tension

Claims

Expectations

1 . Method for joining two joining partners (3) by means of ultrashort laser pulses of a joining beam, preferably for joining at least one joining partner that is essentially transparent for the laser pulses with another joining partner, particularly preferably for joining two joining partners that are transparent for the laser pulses, with one ultrashort laser pulse being more comprehensive Joining beam (1) for local melting of a joining area (11) is introduced into the joining partners (5), characterized in that a process area (21) is heated with at least one process beam (2), the joining beam (1) and the process beam ( 2) are placed next to each other in such a way that the joining area (11) and the process area (21) do not spatially overlap and / or the joining beam (1) and the process beam (2) are designed so that the laser pulses of the process beam (2 ) and the joining beam (1) do not overlap in time.

2. The method according to claim 1, characterized in that the process beam (2) comprises ultrashort laser pulses or continuous wave radiation, the joining beam (1) and the at least one process beam (2) preferably being generated by different lasers and particularly preferably the joining beam (1) is generated by an ultrashort pulse laser and the process beam (2) is generated by a short pulse laser or a continuous wave laser.

3. The method according to claim 1 or 2, characterized in that the at least one process beam (2) has a central spot (23) and at least one further process area

(24) includes.

4. The method according to any one of the preceding claims, characterized in that the profile of the central spot (23) and / or the further process area of the at least one process beam (2) Gaussian, or Bessel-shaped or Laguerre-Gaussian, or is designed as a superposition of the aforementioned.

5. The method according to any one of claims 3 or 4, characterized in that the at least one further process area (24) of the at least one process beam (2) comprises at least one higher order of diffraction. 6. The method according to any one of claims 3 to 5, characterized in that the central spot (23) and the at least one further process area (24) of the at least one process beam (2) are offset longitudinally.

7. The method according to any one of the preceding claims, characterized in that the beam shape of the at least one process beam (2) is generated by means of a beam-shaping unit and / or by means of a spatial light modulator and / or by means of a diffractive element and / or by means of an acousto-optical deflector becomes.

8. The method according to any one of the preceding claims, characterized in that the at least one process beam (2) is moved around the joining beam (1). 9. The method according to claim 8, characterized in that the movement of the at least one process beam (2) is circular or figure-eight, or the trajectory of the movement consists of two touching circles or similar geometries.

10. The method according to any one of the preceding claims, characterized in that in the case of a movement of the joining beam (1) the at least one process beam (2) precedes or follows the joining beam (1), or parallel or with a lateral offset to

Joining beam (1) runs.

11. The method according to claim 10, characterized in that a process beam (2) and a joining beam (1) are provided, and the beams have the same beam intensities.

12. The method according to claim 10, characterized in that two process beams (2) run in front of the joining beam (1) and two process beams (2) follow it and that the process beams (2) are arranged symmetrically around the joining beam (1).

13. The method according to any one of claims 10 or 12, characterized in that the process beams (2) each have approximately one tenth the intensity of the joining beam (1).

14. The method according to any one of claims 8 to 12, characterized in that the movement of the at least one process beam (2) by means of an acousto-optical

Deflector and / or a scanner unit and / or a micro-scanner is generated.

15. The method according to any one of the preceding claims, characterized in that the process beam (2) does not melt the process area (21).