WO2006024585A1

WO2006024585A1 - Laser light source, method for machining workpieces by means of pulsed laser radiation

Info

Publication number: WO2006024585A1
Application number: PCT/EP2005/053723
Authority: WO
Inventors: Hans Jürgen Mayer; Uwe Metka
Original assignee: Hitachi Via Mechanics, Ltd.
Priority date: 2004-09-02
Filing date: 2005-07-29
Publication date: 2006-03-09
Also published as: DE102004042556A1; JP2008511975A; DE102004042556B4; CN1969433A; KR20070047241A

Abstract

The invention relates to a laser light source (110) comprising a laser resonator, whereby the length thereof can be modified by means of a radiation switching device (113), such that the duration of the pulse of the emitted laser radiation can be adjusted according to the respective adjusted resonator length. The radiation switching device (113) can be produced by means of a mechanical mirror system (213). The radiation switching device (113) can also be produced by means of an electro-optical or acusto-optical modulator, such that very fast radiation switching takes place. This enables, even at a high pulse repetition rate, a switching over of the resonator length between two successive laser pulses.The invention also relates to a method for machining workpieces (150) by means of pulsed laser radiation, whereby a laser beam is deviated in a two-dimensional manner by means of a deviation unit (130) and is oriented to the workpiece (150) by means of an optical imaging lens (140). The duration of the pulses of the laser pulse is adjusted, in particular, by selecting the beam path within the laser resonator thereby ensuring optimum material removal.

Description

description

Laser light source, method for processing workpieces by means of pulsed laser radiation

The invention relates to a laser light source, particularly a laser light source for use in a Laserbearbei ^¬ processing machine for drilling and / or patterning of elektro¬ African circuit substrates by pulsed laser radiation. The invention further relates to a method for processing workpieces by means of pulsed laser radiation using the said laser light source.

Electronic assemblies which are to be realized in a compact design, are now often built on more ^¬ layered circuit boards, and in particular mehrschichti¬ gen PCBs. It is necessary that certain conductive layers of the circuit board are contacted with each other. This is usually done by providing a Blind¬ or a through hole is drilled in the contacting layers together into this hole and nachfol ^¬ is quietly provided in a known manner by means of an electrically conductive metallization. In this way, conductor track structures can be formed not only two-dimensionally but also in the third dimension, so that the space requirement of electronic assemblies is considerably reduced.

The drilling of electronic circuit substrates is usually carried out by means of pulsed laser radiation in special laser processing machines for the electronics sector. When

Laser light sources are used, for example, as CO ₂ lasers and solid-state lasers which emit laser radiation having a wavelength in the visible or also in the near ultraviolet spectral range by a frequency multiplication carried out in a known manner. Laser radiation in the ultraviolet spectral range is in particular for the precise removal of metallic layers of a multilayer printed circuit board suitable.

Depending on the material to be processed, the quality of the drilled holes is determined inter alia by the following characteristic parameters of the laser light source used: pulse energy, pulse width, repetition frequency, transverse intensity distribution of the laser beam. Thus, there are a large number of possible combinations of laser parameters for each drilling operation.

To use a material that is optimally edit with great Bearbeitungsge ^¬ speed and with the highest possible quality, a certain set of parameters is most appropriate in each case. Accordingly, different parameter sets are to be regarded as optimal for different materials, with a laser light source usually not being able to achieve all the parameters required for an optimal drilling operation. This problem could be solved by that be incorporated depending on the particular material to be processed different laser light sources in a Laserbearbei ^¬ processing device. Such a conversion of a laser processing machine or the use of a Laserbe ^¬ processing machine with several different types of lasers, however, is very time consuming and very costly.

The invention has for its object to provide a laser light ^¬ source, which emits laser pulses, which ensures optimal material erosion for a variety of different materials. The invention is also the

It is an object of the invention to specify a method for processing workpieces by means of pulsed laser radiation, which generates an optimum material removal for a multiplicity of different materials.

The device-related object is achieved by a laser light source having the features of the independent claim 1. The laser light source according to the invention comprises a laser ^¬ resonator with a partially transmitting Auskoppelspiegel and an end mirror. The laser light source further comprises an active laser medium and a beam switching device, both of which are arranged within the laser resonator. The beam switching device and the laser resonator are set up such that a laser beam guided in the laser resonator can be switched between a first beam path and a second beam path, wherein the second beam path has a different length than the first beam path.

The invention is based on the recognition that the pulse ^¬ wide and varies the pulse duration of the generated laser pulses by changing the cavity length in a simple manner and can thus be adapted to various different materials, so that an optimum, that is both fast and a precise material removal can be achieved. A precise material removal is characterized by the fact that between a region with eroded

Material and another area with unsprayed material is a sharp spatial boundary.

The physical reason for the dependence of the pulse duration on the resonator length can be explained simply by the fact that the propagation time of a light pulse, which requires a predetermined number of passes through the active laser medium to reduce an inversion in the active laser medium, is correspondingly longer with a larger resonator length , The length of a laser pulse thus depends on the transit time within the laser resonator.

Although the end mirror of the laser light source according to the invention preferably a mirror is capable with the highest possible reflection, it should be noted that the Endspie a partially transparent mirror can be ^¬ gel, so that by the inventive laser light source two laser beams be generated, wherein a laser beam, the laser light source from the output mirror and the other laser beam emerges from the partially transparent end mirror.

It is further noted that the invention itself will not ^¬ different to only two Strah ^¬ beam paths is limited within the laser resonator. May be present device depen ^¬ gig on the number of switching positions of Strahlumschalt¬ in principle any number of optical paths of different lengths. Instead of a

Beam switching device with a variety of unterschied¬ union switch positions can also be several Strahlumlenkein¬ directions, each with a plurality of switching positions arranged one behind the other.

In the laser light source according to claim 2, an end mirror is associated with each of the two beam paths, which can be selectively activated by the beam switching device. This means that the beam path within the laser resonator between the beam switching device and the output mirror is fixed independently of the position of the beam switching device. Two beam paths are provided for the beam path between the beam switching device and the end mirror, depending on the position of the beam switching device, wherein exactly one of the two beam paths for guiding the laser beam within the laser resonator is determined by the beam switching device. You can also in this case, not just two, but several end mirrors are used so that in principle arbitrary number of different optical paths direction by a accordingly with entspre ^¬ many switching positions provided Strahlumschaltein¬ activated.

Furthermore, by varying the end position of the respective end mirror, the exact length of a beam path and thus the resulting pulse duration can be set. By a displacement of the coupling-out mirror, the lengths of all beam paths can be changed alike.

The laser light source according to claim 3 has two beam switching elements, which are arranged inside the laser resonator. Between the two beam switching elements, a beam guiding device is provided which, in conjunction with the two beam switching elements, effects a deflection and thus an extension of the current beam path in comparison to the beam path of the so-called zero beam. The zero beam is defined by the beam path in the laser resonator, which results at a certain starting position of the beam switching elements.

Such a "bypass solution", in which the beam path is deflected out of the null beam within a partial region of the laser resonator, thus causes a prolongation of the pulse durations of the emitted laser pulses, depending on the additional length of the beam guiding device. In this case, in principle, any number of "bypass beam paths" are possible, so that the resulting pulse duration can be optimally adapted to a large number of different materials for material processing.

In the embodiment according to claim 4, the beam guiding device has at least one reflector, which contributes to the fact that the laser beam deflected out of the beam path of the zero beam can be returned to the beam path of the zero beam. In this case, the spatial arrangement of the reflector determines the extension of the beam path, so that the resulting pulse duration can be adjusted in a simple manner by a corresponding spatial arrangement of the reflector.

In the embodiment according to claim 5, the laser beam guided in the laser resonator is emitted from the null beam by the first of the two beam switching elements. deflects and coupled ^¬ in a first end of an optical waveguide ^¬ . After passing through the optical waveguide, the light beam leaves the other end of the Lichtwellenlei ^¬ ters and is at a symmetrical switching position of the two beam switching over the second of the two

Beam switching elements again transferred into the beam path of the zero ^¬ beam. Can be the length of the optical waveguide in this case determines the extension of the beam path of the laser resonator ^¬ gate, so that the "bypass optical path" through a comparatively low on adjustment realized.

According to claim 6, the beam switching device has a rotatably mounted mirror or a chopper device. The beam path within the laser resonator can thus be realized via a mechanical movement of conventional optical components. For such a mechani¬ ULTRASONIC switching between different beam paths inner¬ half of the laser resonator a greater period of time is at least rates of large repeat ^¬ required as the time interval between two consecutive laser pulses in the rule. Thus, the resulting pulse length of the individual laser pulses can not be varied individually, but only for a sequence of a plurality of laser pulses. However, the use of such mechanical beam switching devices is easy to implement and completely sufficient for a large number of applications, since as a rule a material having a multiplicity of successive laser pulses is processed with an unchanged pulse duration.

As a chopper, for example, is a rotatably mounted glass, which alternately transparent and mirrored areas, which are introduced into the beam path and thus alternately cause transmission and reflection. When using a rotatably mounted mirror is particularly suitable a rotary mechanism in which the mirror between different, precisely defined angular positions can be switched. The embodiment according to claim 7 has as Strahlumschalt¬ device on an electro-optical modulator or an acousto-optical modulator. In the beam switching means of an electro-optic modulator of modu lator ^¬ causes rotation of the polarization of the light beam. The spatial separation of the differently polarized laser beams then takes place with a polarization-sensitive reflector, for example a so-called Brewster window. An acousto-optic modulator is, for example, a CdTe

Crystal, which is excited with a frequency in the megahertz range to mechanical vibrations. The stationary wave formed within the crystal represents a diffraction grating for an incident laser beam.

A beam switching with electroacoustic or with acousto-optical modulators has the advantage that the switching can be done very quickly, so even switching the laser resonator between different beam paths even at a laser pulse repetition rate in the range of several kHz in principle between two successive following laser pulses is possible. Such targeted variation of the pulse duration of individual laser pulses results in a large number of new possibilities for optimal material processing. By way of example, the material processing can take place by means of a plurality of successive laser pulses at one and the same point, wherein the pulse duration of a laser pulse differs from the pulse duration of the laser pulse previously directed to the same location.

It should be noted at this point that a deflection of the laser beam guided in the laser resonator can be carried out selectively into one of a multiplicity of radiation paths of different lengths, also by means of a series connection of a plurality of beam deflecting devices. In this case, several identical beam deflecting devices or even different types of Strahlumlenkeinrichtungen be combined.

The embodiment of claim 8, wherein the active laser medium is a solid material, preferably with ^¬ means of Nd: YAG, Nd: YVO ₄ -, or Nd: YLF lasers realized which typically emit laser beams at a fundamental wavelength of 1064 nm ,

In the embodiment according to claim 9, the pumping of the active laser medium takes place optically using semiconductor diodes. These are preferably arranged around the active laser medium, so that a corresponding diode-pumped laser, in particular a diode-pumped solid-state laser, can be realized in a compact design.

According to claim 10, the laser light source in addition to an optically non-linear medium for frequency multiplication. Such optically non-linear media, which are generally known in laser technology, can be positioned both inside and outside the resonator. In any of the above types of laser with a fundamental wavelength of 1064 nm is frequency-multiplied radiation having wavelengths of 532 achieved nm, 355 nm and 266 nm. Such a frequency multiplier, in which the fundamental wavelength hal ^¬ beer, is divided into thirds or quarters is to be considered as exemplary only , A frequency multiplication by a factor of 5, 6 or more is particularly modern Lasersys ^¬ temen also conceivable. The frequency multiplier has the advantage that in a simple manner cash laser radiation in the visible or ^¬ may also generate the ultraviolet spectral range, which are particularly well suited for the removal of metallic layers, such as copper.

The object underlying the invention procedural Aufga ^¬ be is achieved by a method for processing workpieces by means of pulsed laser radiation having the features len of the independent claim 11. In the method according to the invention, a laser beam is generated by means of a laser light source, which laser pulses each having a specific pulse duration. The generated laser beam is deflected two-dimensionally by means of a deflection unit and directed to predetermined target positions on the workpiece by means of imaging optics. The pulse durations are selected depending on the material of the workpiece such that an optimal material removal is ensured. At an optimum material removal both a schnel¬ ler as well as a precise as possible material removal is hen To Hide ^¬ in this context. Precise material removal results in a sharp, well-defined spatial boundary between a region of abraded material and an area of uncut material. The optimal pulse duration can be determined in advance of the real laser processing depending on the respective material to be processed by a few experiments.

According to claim 12, a laser light source according to any one of claims 1 to 10 is used to generate the pulsed laser beam. The beam switching device and thus the beam path of the laser beam within the laser resonator are adjusted such that the workpiece is subjected to laser pulses with the corresponding pulse duration. By a comparatively easy to implement change in the length of the laser resonator thus the pulse durations can be optimized for each material to be processed. Since very high requirements with regard to the precision of material processing must be met in the electronics sector due to the increasing miniaturization of electronic assemblies, the invention can be used in particular for drilling or structuring electronic circuit carriers.

Further advantages and features of the present invention will become apparent from the following exemplary description of presently preferred embodiments. In the drawing in schematic drawings Figure 1 show a laser processing machine having a laser light source ^¬ which different lengths of optical paths having within the laser resonator,

Figure 2a, 2b and 2c a laser light source, are realized in the under ^¬ different length optical paths within the Laserre ^¬ sonators by a folding mirror and correspondingly positioned end mirrors, Figure 3 ment a laser light source with a Strahlumschaltele ^¬ which a laser beam selectively to below ^¬ schiedliche end mirror steers,

FIG. 4 shows a laser light source with two beam switching ^elements which can direct a laser beam into the region between the two beam switching elements on different beam paths, to each of which an optical waveguide is assigned,

Figure 5 shows a laser light source with two Strahlumschaltelemen ^¬ th, which can direct a laser beam in the area between the two beam switching on unterschiedli¬ che beam paths, each associated with a reflector, and Figure 6 shows the structure of a beam switching element of an electro-optical modulator and a Brewster window.

It should be noted at this point that in the drawing, the reference symbols of corresponding components differ only in their first digit. For this reason, some components already explained are not described again with reference to other figures.

The laser processing machine 100 shown in FIG. 1 comprises a laser light source 110, which is set up to emit a pulsed output laser beam 121.

This applies to a deflection unit 130, which in Licher herkömm ^¬ manner with rotatably mounted mirrors, so called. Galvospie- is constructed. The deflection unit 130 permits a two-dimensional deflection of the laser beam, which is directed onto the substrate 150 to be processed via an imaging optical system 140, for example an F-theta optical system.

In the example shown, the substrate 150 consists of a dielectric layer 151, which is covered by a metallic layer 152 on the upper side and underside, respectively. The metallic layers 152 are structured in a manner not shown to form interconnects. To produce the

Microholes 153, a processing laser beam 141, which has emerged from the output laser beam 121 by a deflection by the deflection unit 130 and focusing by the imaging optics 140, each centered by a jump motion 155 to a drilling position 144 and then with a set on the imaging optics 140 spot size F in the region of the drilling position 154 in a circular movement, so that in each case a micro hole is generated. Depending on the given conditions (substrate material, hole depth, laser power, etc.) is thereby the Bearbeitungsla ^¬ moved in a circulating or in several successive revolutions serstrahl 141st In such a Bohrverfah¬ Ren, which is referred to as trepaning, thus the laser beam 141 is guided only along the edge of the hole and the inner core cut out. In this way, holes are drilled which are larger than the spot size F, respectively. In the production of microholes, it may also be necessary to perform several revolutions of the laser beam 141 with the same or different radii.

According to the invention it is now provided that is the laser light source ^¬ formed such that in the output laser beam 121 ^¬ laser pulses can be generated er¬ with different pulse durations. This is realized, for example, by the structure described below, the laser light source 110. The laser light source 110 comprises a Laserreso ^¬ nator which an output mirror 112 and a plurality of end mirror, having a first end mirror 114a, a second 114b Endspie ^¬ gel and a third end mirror 114c. Inner ^¬ half of the laser resonator, an active laser medium 111 is arranged, which is in particular a solid state material such as Nd: YAG or Nd: YVO ₄ . In the laser resonator a Strahlumschaltelement 113 is further arranged which se a beam path 115 within the laser resonator alterna ^¬ in a beam path of the three beam paths, in a first Strah¬ 115a, transferred to a second optical path 115b or in a third optical path 115c. In each case, one of the beam paths 115a, 115b or 115c is assigned an end mirror 114a, 114b or 114c. The end mirrors 114a, 114b and 114c are arranged at different distances from the beam switching element 113, so that one of the beam paths 115a, 115b or 115c is activated depending on the control of the beam switching element 113.

The Strahlumschaltelement 113 may be a mechanical mirror ^¬ system or an electrically controllable modulator very quickly, for example an acousto-optical modulator or, in particular an electro-optical modulator to be. A possible structure of a jet switching element will be described later with reference to FIG.

It should be noted at this point that, in particular when using an acousto-optic modulator as beam switching element, a reflector can additionally be connected downstream of the modulator. With a corresponding angular position of the reflector relative to the beam path of the deflected beam, the resulting deflection angle can thus be significantly increased in comparison to the usually very small deflection angles, which can be achieved with a modulator. Thus deflection angles in the range of 90 ° can be realized even when using an acousto-optical modulator.

As can be seen from FIG. 1, the beam paths 115a, 115b and 115c have a different length. Thus, the The effective resonator length can be set as a function of the position of the beam switching element 113 between three different lengths, so that, as a result, the pulse durations of the output laser beam 121 depend on the position of the beam switching element 113.

The dependence of the pulse duration on the resonator length can be explained by the fact that a laser pulse lasts until the inversion in the active laser medium 111 is degraded. This means that the majority of the excited atoms or molecules in the active laser medium 111 are again in their ground state. Since a certain number of passes of a light pulse through the active medium 111 is required for reducing the inversion, there is no need to further explain that the total time required for a light pulse for this number of passes depends on the resonator ^length .

FIGS. 2 a, 2 b and 2 c show a further exemplary embodiment of the invention, in which the jet ^switching element is realized by means of a rotatably mounted mirror 213. The laser light source, which emits a pulsed output laser beam 221 via a coupling-out mirror 212, has as active laser medium 211 a solid-state material, in particular Nd: YAG or Nd: YVO ₄ . In the first position of the rotatably mounted mirror 213 shown in Figure 2a, the laser resonator is gebil ^¬ det only by the Auskoppelspiegel 212 and serving as the first end mirror 214a mirror 213. Within the laser resonator, the laser beam thus extends only on a beam path 215 which is delimited by the rotatable mirror 213 serving as the first end mirror 214a and the outcoupling mirror 212.

In a tilting of the rotatably mounted mirror 213 by 45 ° clockwise about a plane perpendicular to the plane of rotation axis, a laser beam in the beam path 215 by a reflection on the mirror 213 to a stationary second end mirror 214, so that the laser beam within the laser resonator along the beam paths 215 and 215 b extends. The resonator length is thus lengthened by the length of the beam path 215b compared with the resonator length shown in FIG. 2a.

In the case of a mirror position of the rotatably mounted mirror 213, as shown in FIG. 2a, by a rotation angle of 45 ° in the counterclockwise direction, the beam path illustrated in FIG. 2c results within the laser resonator. The laser resonator is formed by the Auskoppel¬ mirror 212 and the third end mirror 214c, which is spaced from the mirror 213 farther than the second end mirror 214b. The resulting resonator length is therefore composed of the length of the beam path 215 and the length of the third beam path 215c.

By varying the angular position of the rotatably mounted mirror 213 and a corresponding arrangement of the second end mirror 214b and the third end mirror 214c relative to the mirror 213, the resonator length of the laser light source 210 can thus be varied in a simple manner and thus the resulting pulse length of the laser pulses of the output laser ^¬ beam 221 can be optimally adapted to the respective material to be machined.

The embodiment shown in Figure 3 differs from that shown in Figures 2a, 2b and 2c

Embodiment in that instead of the rotatably mounted mirror 213, an electrically controllable Strahlumschaltele ^¬ ment 313 is provided. This transferred the optional lengängen of four Strah¬ between the Strahlumschaltelement 313 and the output mirror 212 ver ^¬ current beam path 315 in a, which are provided with the reference numerals 315a, 315b, 315c or 315d. The beam paths 315a, 315b, 315c and 315d are each an end mirror 314a, 314b, 314c and 314d associated with the four end mirrors are arranged at different distances from the beam switching element 313.

The laser light source 410 shown in FIG. 4 differs from the laser light source 310 in that only one end mirror 414 is provided which, together with the outcoupling mirror 412, forms the laser resonator of the laser light source 410. Within the laser cavity in addition to the active laser medium 411 Strahlumschaltelemente two, a first 413a and a second Strahlumschaltelement Strahlum ^¬ are arranged switching element 413b. With an appropriate control of the two Strahlumschaltelemente 413a, 413b, a guided within the laser resonator laser ^¬ beam runs between the two modulators selectively in one of four beam paths, which are provided with the reference numerals 415a, 415b, 415c or 415d. The beam paths 415b, 415c and 415d respectively extend over an optical waveguide 416b, 416c and 416d, which have a different length to one another. Thus, depending on the position of the two beam switching elements 413a and 413b, which are always switched symmetrically to each other, the resulting resonator length of the laser light source 410 changed such that the laser pulses of the output laser beam 421 can be optimally adjusted in terms of their pulse duration to the respective material to be processed.

The laser light source shown in FIG 5510 under failed ^¬ det from the laser light source 410 in that is provided in place of the three optical waveguide 416b, 416c and 416d, respectively, a stationary reflector 517b, 517c or 517d. In the case of a symmetrical activation of the two beam switching elements 513a and 513b, the laser beam within the laser resonator can thus be guided selectively onto the beam path 515a or onto one of the deflected beam paths 515b, 515c or 515d. FIG. 6 shows the construction of a beam switching element 613, which has an electro-optical modulator 660 and a Brewster window 663. The incident laser beam 615 is linearly polarized. By a corresponding control of the electro-optical modulator 660 by means of a control unit, not shown, the polarization direction of an emerging from the modulator 660 laser beam 662 along the direction of rotation 661 can be varied so that the laser beam 662 in a first position of the electro-optical modulator 660 parallel to the plane of the drawing and in a second position is polarized perpendicular to the plane of the drawing.

The Brewster window 663 is arranged in the beam path of the laser beam 662 in a Brewster geometry familiar to the person skilled in the art, so that in the first position of the electro-optical modulator 660 the laser beam 662 has a parallel offset into the beam path 615b determined by the thickness and the refractive index of the Brewster window 663 is transferred. In the second position of the electro-optical modulator 660, the laser beam 662, which is polarized perpendicular to the plane of the drawing, is transferred into the beam path 615a. By a corresponding control of the electro-optical modulator 660, the input laser beam 615 can thus be selectively converted into one of the two beam paths 615a and 615b.

For selective beam switching in more than two output beam paths, it goes without saying that a plurality of beam switching elements 613 can be connected in series in a cascade.

At this point it should be noted that application in Ver¬ of acousto-optical modulators in a Strahlum- switching element, the deflection angles usually are very small, so that without the additional use of appropriately arranged ^¬ Umlenkreflektoren the changes of the resonator are low. Larger changes in length can be realized in an advantageous manner by the use of a plurality of reflectors arranged in parallel, between which the respective deflected laser beam can be reflected back and forth several times. In this way, a significant variation of the resulting resonator length can be realized within a compact optical design.

In summary, it can be stated that the invention provides a laser light source 110 with a

Laser resonator, the length of which by means of a Strahlumschaltein¬ device 113 is changed, so that the pulse duration of the emit ^¬ oriented laser radiation can be adjusted depending on the in each case preset resonator length. The beam switching device 113 can be realized by means of a mechanical mirror system 213. The beam switching device 113 can also be realized by means of an electro-optical or acousto-optical modulator, so that the beam switching can take place very quickly. This makes it possible to switch over even with a high pulse repetition rate

Resonator length between two successive Laserpul¬ sen. The invention further provides a method for machining workpieces 150 by means of pulsed laser radiation, wherein a laser beam is deflected two-dimensionally by means of a deflection unit 130 and is directed onto the workpiece 150 via imaging optics 140. The pulse duration of the laser pulses is adjusted in particular by a choice of the beam path within the laser resonator such that an optimal material removal is ensured.

Claims

claims

1. Laser light source, in particular for use in a laser processing machine for drilling and / or structuring of electronic circuit carriers by means of pulsed laser radiation, with

A laser resonator, which has a partially transmitting output mirror (112) and an end mirror (114a, 114b, 114c), an active laser medium (111), which is arranged inside the laser resonator, and

• A beam switching device (113), which is also arranged within the laser resonator, wherein the beam switching device (113) and the laser resonator are arranged such that a guided in the laser ^¬ resonator laser beam between a first Strah¬ lengang (115 a) and a second beam path (115b) is um¬ switchable, wherein the second beam path (115b) has a different compared to the first beam path (115a) length.

The laser light source according to claim 1, wherein the laser resonator has a first end mirror (114a) and a second end mirror (114b) disposed relative to the beam switching means (113) such that

• the first beam path (115, 115a) between the Auskoppel¬ mirror (112) and the first end mirror (114a) and

• the second beam path (115, 115b) extends between the Auskoppel¬ mirror (112) and the second end mirror (114b).

3. Laser light source according to claim 1,

In which the beam switching device has a first beam switching element (413a) and a second beam switching element (413b), both of which are arranged inside the laser resonator, and

In which additionally a beam guiding device (415b, 415c, 415d) is provided, which is relative to the two Beam switching elements (413a, 413b) is arranged such that at a corresponding position of the two Strahlum¬ switching elements (413a, 413b) between the Auskoppelspie ^¬ gel (412) and the end mirror (414) guided laser beam via the beam guiding device (415b, 415c, 415d).

4. Laser light source according to claim 3, wherein the Strahlfüh¬ tion device at least one reflector (517b, 517c, 517d).

5. Laser light source according to one of claims 3 to 4, wherein the beam guiding device has at least one Lichtwellenlei¬ ter (416b, 416c, 416d).

6. Laser light source according to one of claims 1 to 5, wherein the beam switching device at least

• a rotatably mounted mirror (213) and / or

• has a chopper device.

7. Laser light source according to one of claims 1 to 6, wherein the beam switching device

An electro-optical modulator (660) and / or an acousto-optic modulator.

8. Laser light source according to one of claims 1 to 7, wherein the active laser medium is a solid state (111).

9. Laser light source according to one of claims 1 to 8, wherein at least one semiconductor diode for pumping the active laser ^¬ medium (111) is provided.

10. Laser light source according to one of claims 1 to 9, wherein in addition an optically non-linear medium for Frequenz¬ multiplication is provided.

11. Method for processing workpieces by means of pulsed laser radiation, in particular for drilling and structuring electronic circuit carriers, in which a laser beam (121) is generated by means of a laser light source, which has laser pulses each having a specific pulse duration, and

• The laser beam (121) by means of a deflection unit (130) deflected two-dimensionally and via an imaging optics (140) to predetermined target positions on the workpiece

(150) is directed, wherein the pulse durations depending on the material of the workpiece (150) are selected such that an optimal material removal is ensured.

12. The method of claim 11, wherein the laser beam (121) by means of a laser light source (110) according to one of claims 1 to 10 is generated, and the beam switching device (113) and thus the Strahlen¬ gear (115, 115a, 115b, 115c ) of the laser beam within the laser resonator are set such that the workpiece (150) is hit with laser pulses having the corresponding pulse duration.