WO2005032758A1 - Method for operating a gas laser system - Google Patents

Method for operating a gas laser system Download PDF

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Publication number
WO2005032758A1
WO2005032758A1 PCT/EP2004/050555 EP2004050555W WO2005032758A1 WO 2005032758 A1 WO2005032758 A1 WO 2005032758A1 EP 2004050555 W EP2004050555 W EP 2004050555W WO 2005032758 A1 WO2005032758 A1 WO 2005032758A1
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WO
WIPO (PCT)
Prior art keywords
laser
phase
resonator
pulse
during
Prior art date
Application number
PCT/EP2004/050555
Other languages
German (de)
French (fr)
Inventor
Alexander Kilthau
Hans Jürgen MAYER
Petra Mitzinneck
Original Assignee
Hitachi Via Mechanics, Ltd.
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Application filed by Hitachi Via Mechanics, Ltd. filed Critical Hitachi Via Mechanics, Ltd.
Priority to JP2006530165A priority Critical patent/JP2007507870A/en
Publication of WO2005032758A1 publication Critical patent/WO2005032758A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B23K26/0622—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam by shaping pulses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring

Definitions

  • the invention relates to a method for operating a laser system for processing substrates with a gas laser, in particular a CO 2 laser, in which in a gas-filled laser resonator, to which a high-frequency voltage for generating a predetermined pump power is applied during a respective working phase and in which a pulsed laser beam with a predetermined repetition frequency is generated by means of a good switch, which is directed to a processing position by a deflection unit, generates a predetermined number of pulses there during a working phase and is then directed to a next processing position by the deflection unit in a jump phase, whereby during the jump phase from one processing position to the next, the laser beam is switched off and does not emit any pulses to the outside.
  • a gas laser in particular a CO 2 laser
  • a gas-filled laser resonator to which a high-frequency voltage for generating a predetermined pump power is applied during a respective working phase and in which a pulsed laser beam with a predetermined repetition frequency is generated by means of
  • DE 10145184 AI describes a method for laser drilling holes in a circuit substrate, in which a CO ? -Laser is used.
  • a CO ? -Laser When drilling circuit boards with CO 2 lasers, a certain application-dependent number of laser pulses is required per hole.
  • Such a pulse sequence is also called a burst.
  • the duty cycle from the time in which pulses with a defined pulse frequency are emitted to the time in which no pulses are emitted is also called the duty cycle. This duty cycle must not exceed a characteristic value, because otherwise the available lasers are given the high pulse power the cooling of the gas can no longer take place and thus the efficiency drops.
  • WO 02/082596 A2 describes a CO ? -Laser source described for such applications in which the resonator with a
  • Cow device For the energy conditions in the resonator during a respective pulse sequence, the cooling can be set so that the temperature or energy conditions in the resonator are kept at the same level and the pulses within this pulse sequence are also of the same size. However, it should be noted that if the number of pulses in a pulse sequence is too high, the pulse height drops.
  • the aim of the invention is therefore to modify a method of the type mentioned in the introduction in such a way that even with different distances between the processing positions and correspondingly different switch-off times of the laser beam loss of time allows a constant processing quality at all processing positions.
  • this aim is achieved in that the high-frequency pump voltage is applied intermittently to the laser resonator during the jump phases in such a way that the energy level in the resonator is kept at approximately the same level as during the working phases.
  • the duty cycle or the duty cycle between pulse sequences and pulse pauses is kept approximately the same even in the times of laser shutdown, so that the cooling of the gas is also controlled in a defined manner and thus the energy level in the resonator even during the breaks. This means that when the laser is switched on again, pulses of the same level as in the previous pulse sequence can be emitted immediately.
  • the resonator can be controlled with the high-frequency pump voltage during the jump phases in different variants. It is thus possible to continuously modulate the high-frequency voltage during these jump phases. But it is also possible for a defined switch-off time at the beginning and / or at the end of the
  • the method according to the invention can be expanded in such a way that the modulation of the high-frequency voltage not only during the jump phases when processing a specific processing field, but also during longer breaks, for example when changing from one processing field to a next or when the system is in a standby operating state is continued at the resonator.
  • Various criteria, in particular the properties of the special laser resonator, must be taken into account in order to determine the necessary duty cycle in the modulation according to the invention.
  • This duty cycle is therefore preferably determined experimentally by, for example, drilling at different pulse-pause ratios of the high-frequency voltage with the laser switched off, and examining the quality of the holes.
  • it is also possible to determine the energy level prevailing in the resonator by emitting test pulses from the laser and measuring the pulse heights. The pulse heights can be measured by means of a photodiode or the like.
  • FIG. 1 shows a schematic representation of a gas laser system for the application of the method according to the invention
  • FIG. 2 shows the various signals effective for generating laser pulses in the laser resonator
  • FIGS. 4, 5 and 6 corresponding time diagrams with the control pulses for the laser resonator in the method according to the invention in three different variants.
  • FIG. 1 shows a laser system for a method according to the invention.
  • a resonator 1 with a gas mixture, preferably with CO ? , filled chamber is provided, to which a high-frequency voltage RF is applied via an electrode system 2.
  • the resonator 1 is also cooled via a cooling system 3 with corresponding coolant connections.
  • a good switch 4 in the form of an electro-optical modulator arrangement, which is supplied with high-frequency voltage via a corresponding pulse control 5, a mirror arrangement, likewise only shown schematically, is used 6 pulses sent through a window 7 into the resonator 1 and passed there via further mirror arrangements 8.
  • a clever arrangement of the mirrors in a small space increases the effective length of the active resonator.
  • laser pulses LP are generated, which are directed via an output window 9 out of the resonator and via a deflection unit 10 with movable mirror arrangements onto a workpiece 11 in order to machine this workpiece there, for example to drill holes, at the respective working positions.
  • the workpiece 11 is arranged on an adjustable table 12, whereby certain machining fields of the workpiece can be brought into the area of the laser beam.
  • Both the table 12 and the deflection unit 10 are controlled by a positioning system 13, which in turn is controlled by a central control unit 14.
  • This central control unit 14 also coordinates the high-frequency voltage RF at the resonator and the generation of the pulses via the good switch 4 or its control 5.
  • This system according to FIG. 1 is known and is described with its essential elements in WO 02/082596 A2.
  • FIG. 2 shows the pulse diagram of a system according to FIG. 1 in a conventional operating mode.
  • the control device 14 applies the high-frequency voltage RF to the resonator at time tbl, which is in the excitation state for the duration of this applied voltage. If the control device 5 then applies trigger pulses TP to the good switch 4, the resonator emits a corresponding pulse sequence of laser pulses LP.
  • Figure 3 shows a corresponding pulse sequence when drilling holes at different distances on a circuit board (in Figures 3 to 6, all signals are shown, for example, low active; of course, a representation with high active would also be possible).
  • An example is shown in which individual work phases APH1, APH2 and APH3 each serve to drill a hole, while between the work phases each because jump phases SPH1 and SPH2 enable the beam deflection to jump from the first hole to the second, etc.
  • the jump phases are of different lengths since the distances between the holes to be drilled are different. In practice, this involves, for example, distances of the order of 200 ⁇ m to 50 mm, with a jump taking about 200 ⁇ s to 300 ms.
  • FIG. 3 shows a corresponding pulse sequence when drilling holes at different distances on a circuit board (in Figures 3 to 6, all signals are shown, for example, low active; of course, a representation with high active would also be possible).
  • An example is shown in which individual work phases APH1, APH2 and
  • FIG. 4 shows a first example of an operating mode according to the invention.
  • the triggering of the laser is deactivated via the good switch in the jump phases as before in the conventional method.
  • the RF (radio frequency) power is applied intermittently over the entire jump phase with a predetermined duty cycle from tl to t2, so that the overall ratio of the jump phases SPH to the working phases APH ("RF power OFF" to "RF power ON ”) is balanced. This compensates for the voltage phase SPH, which is larger in comparison to the working phase APH, and a balanced energy level is achieved.
  • FIG. 5 shows a somewhat modified embodiment with the same lengths of the working phases APH1 to APH3 and the intermediate jumping phases SPH1 and SPH2 as in the previous example.
  • the intermittent modulation of the RF power is designed right at the beginning of the jump phase.
  • the excitation of the resonator is permanently switched off or on for a predetermined pause time PZ with the length t3 until the start of the next working phase.
  • FIG. 6 in another variant it is possible to start the jump phase SPH1 or SPH2 with a defined pause time PZ of length t3 or different lengths and then to start the intermittent RF power until the start of the next work phase put on the resonator. It is also possible to combine the variants of FIGS.
  • the laser pulse sequences LPF1, LPF2 and LPF3 and the resulting work phases APH1, APH2 and APH3 can also be of different lengths.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Electromagnetism (AREA)
  • Lasers (AREA)

Abstract

The invention relates to a method for operating a gas laser system, especially with a CO2 laser. Predetermined pulse sequences (LPF1, LPF2, LPF3) are directed in a working phase (APH1, APH2, APH3) to a determined processing point of a substrate, and then laser deflection is adjusted onto the next working point in a transfer phase (SPH1, SPH2). High frequency pump energy (RF) is applied to the laser resonator in an intermittent manner during the transfer phase (SPH1, SPH2) in order to prevent variable cooling of the laser resonator and also varying hole qualities in the holes made by the laser due to uneven distances between the processing points and corresponding uneven long transfer phases, such that the power level in the resonator is maintained at approximately the same level as during the working phases (APH1, APH2, APH3).

Description

Beschreibungdescription
Verfahren zum Betrieb eines GaslasersystemsMethod for operating a gas laser system
Die Erfindung betrifft ein Verfahren zum Betrieb eines Lasersystems zur Bearbeitung von Substraten mit einem Gaslaser, insbesondere einem Cθ2~Laser, bei dem in einem gasgefullten Laserresonator, an welcher eine Hochfrequenzspannung zur Erzeugung einer vorgegebenen Pumpleistung wahrend einer jewei- ligen Arbeitsphase anliegt und in welcher mittels eines Guteschalters ein gepulster Laserstrahl mit einer vorgegebenen Wiederholfrequenz erzeugt wird, der durch eine Ablenkeinheit jeweils zu einer Bearbeitungsposition gelenkt wird, dort wahrend einer Arbeitsphase eine vorgegebene Anzahl von Pulsen erzeugt und dann mittels der Ablenkeinheit in einer Sprungphase zu einer nächsten Bearbeitungsposition gelenkt wird, wobei jeweils wahrend der Sprungphase von einer Bearbeitungsposition zu einer nächsten der Laserstrahl abgeschaltet wird und keine Pulse nach außen abgibt.The invention relates to a method for operating a laser system for processing substrates with a gas laser, in particular a CO 2 laser, in which in a gas-filled laser resonator, to which a high-frequency voltage for generating a predetermined pump power is applied during a respective working phase and in which a pulsed laser beam with a predetermined repetition frequency is generated by means of a good switch, which is directed to a processing position by a deflection unit, generates a predetermined number of pulses there during a working phase and is then directed to a next processing position by the deflection unit in a jump phase, whereby during the jump phase from one processing position to the next, the laser beam is switched off and does not emit any pulses to the outside.
Derartige Verfahren zur Bearbeitung von Substraten sind bekannt. Beispielsweise ist in der DE 10145184 AI ein Verfahren zum Laserbohren von Lochern in einem Schaltungssubstrat beschrieben, bei dem vorzugsweise ein CO?-Laser verwendet wird. Beim Bohren von Leiterplatten mit Cθ2~Lasern wird pro Loch eine bestimmte applikationsabhangige Anzahl von Laserpulsen benotigt. Eine solche Pulsfolge wird auch Burst genannt. Für eine gleichbleibende und reproduzierbare Lochqualitat ist es notwendig, daß sowohl der Verlauf der Pulshohe in einer Puls- folge wie auch die absolute Pulshohe von einer Pulsfolge zur nächsten Pulsfolge identisch sind. Das Tastverhai tnis von der Zeit, in der Pulse mit einer definierten Pulsfrequenz emittiert werden, zu derjenigen Zeit, in der keine Pulse emittiert werden, wird auch Duty Cycle genannt. Dieser Duty Cycle darf einen charakteristischen Wert nicht überschreiten, da bei der hohen Pulsleistung der verfugbaren Laser ansonsten das Abkühlen des Gases nicht mehr erfolgen kann und damit die Effizient sinkt.Such methods for processing substrates are known. For example, DE 10145184 AI describes a method for laser drilling holes in a circuit substrate, in which a CO ? -Laser is used. When drilling circuit boards with CO 2 lasers, a certain application-dependent number of laser pulses is required per hole. Such a pulse sequence is also called a burst. For a constant and reproducible hole quality, it is necessary that both the course of the pulse height in one pulse sequence and the absolute pulse height from one pulse sequence to the next pulse sequence are identical. The duty cycle from the time in which pulses with a defined pulse frequency are emitted to the time in which no pulses are emitted is also called the duty cycle. This duty cycle must not exceed a characteristic value, because otherwise the available lasers are given the high pulse power the cooling of the gas can no longer take place and thus the efficiency drops.
In der WO 02/082596 A2 ist eine CO?-Laserquelle für solche Anwendungen beschrieben, bei der der Resonator mit einerWO 02/082596 A2 describes a CO ? -Laser source described for such applications in which the resonator with a
Kuhleinrichtung versehen ist. Für die Energieverhaltnisse in dem Resonator wahrend einer jeweiligen Pulsfolge kann die Kühlung so eingestellt werden, daß die Temperatur- bzw. Energieverhaltnisse in dem Resonator auf gleichem Niveau gehalten werden und dadurch auch die Pulse innerhalb dieser Pulsfolge gleich groß sind. Zu beachten ist trotzdem, daß bei zu hoher Anzahl von Pulsen in einer Pulsfolge die Pulshohe absinkt.Cow device is provided. For the energy conditions in the resonator during a respective pulse sequence, the cooling can be set so that the temperature or energy conditions in the resonator are kept at the same level and the pulses within this pulse sequence are also of the same size. However, it should be noted that if the number of pulses in a pulse sequence is too high, the pulse height drops.
Probleme treten allerdings dann auf, wenn bei einem Bohrpro- gramm die Abstände der Locher zueinander unterschiedlich sind, wodurch auch unterschiedlich lange Sprungphasen zwischen den Pulsfolgen liegen, in denen der Laser entsprechend unterschiedlich lang abgeschaltet wird. Dies hat zur Folge, daß in einem hohen Leistungsbereich durch die unterschiedlich lange Abkuhlzeit des Gases im Laserresonator die Effizienz und damit die Leistung der Pulse von Pulsfolge zu Pulsfolge unterschiedlich sind. Dies beeinträchtigt entsprechend die Reprodu7ierbarkei t der Lochqual itat . Es wäre zwar möglich, die nachteilige Wirkung der ungleichen Bewegungszeiten von Loch zu Loch durch entsprechende zusatzliche Wartezeiten auszugleichen und so immer gleiche Zeitabstande zwischen den Pulsfolgen zu gewahrleisten. Das hatte jedoch zur Folge, daß man zwischen den Pulsfolgen immer das größtmögliche Intervall annehmen mußte. Damit wurde derProblems do occur, however, when the distances between the holes are different in a drilling program, which means that there are jump phases of different lengths between the pulse sequences in which the laser is switched off for different lengths. As a result, the efficiency and thus the power of the pulses differ from pulse train to pulse train in a high power range due to the differently long cooling time of the gas in the laser resonator. This affects the reproducibility of the hole quality accordingly. It would be possible to compensate for the disadvantageous effect of the unequal movement times from hole to hole by means of corresponding additional waiting times and thus always to ensure the same time intervals between the pulse sequences. However, this meant that the largest possible interval had to be assumed between the pulse sequences. With that, the
Bohrprozeß insgesamt sehr langsam mit einem entsprechend sinkenden Durchsatz.Overall, the drilling process is very slow with a correspondingly falling throughput.
Ziel der Erfindung ist es deshalb, ein Verfahren der eingangs genannten Art so zu modifizieren, daß auch bei unterschiedlichen Abstanden der Bearbeitungspositionen und entsprechend unterschiedlichen Abschaltzeiten des Laserstrahls ohne zu satzlichen Zeitverlust eine gleichbleibende Bearbeitungsqua- litat an allen Bearbeitungspositionen ermöglicht wird.The aim of the invention is therefore to modify a method of the type mentioned in the introduction in such a way that even with different distances between the processing positions and correspondingly different switch-off times of the laser beam loss of time allows a constant processing quality at all processing positions.
Erfindungsgemaß wird dieses Ziel dadurch erreicht, daß die Hochfrequenz-Pumpspannung wahrend der Sprungphasen derart intermittierend an den Laserresonator angelegt wird, daß das Energieniveau in dem Resonator auf annähernd der gleichen Hohe gehalten wird wie wahrend der Arbeitsphasen. Mit der erfindungsgemaßen definierten Ansteuerung der Hochfrequenzspannungen an dem Laserresonator wird das Tastver- haltnis bzw. der Duty Cycle zwischen Pulsfolgen und Pulspausen auch in den Zeiten der Laserabschaltung etwa gleich gehalten, so daß auch die Abkühlung des Gases definiert ge- steuert wird und so das Energieniveau in dem Resonator auch wahrend der Pausen gleichgehalten wird. So können beim Wiedereinschalten des Lasers sofort Pulse in gleicher Hohe wie bei der vorherigen Pulsfolge abgegeben werden. Die Ansteuerung des Resonators mit der Hochfrequenz- Pumpspannung wahrend der Sprungphasen kann in unterschiedlichen Varianten erfolgen. So ist es möglich, wahrend dieser Sprungphasen eine fortlaufende Modulation der Hochfrequenz- spannung durchzufuhren. Es ist aber auch möglich, für eine definierte Abschaltzeit zu Beginn und/oder zum Ende derAccording to the invention, this aim is achieved in that the high-frequency pump voltage is applied intermittently to the laser resonator during the jump phases in such a way that the energy level in the resonator is kept at approximately the same level as during the working phases. With the defined control of the high-frequency voltages on the laser resonator according to the invention, the duty cycle or the duty cycle between pulse sequences and pulse pauses is kept approximately the same even in the times of laser shutdown, so that the cooling of the gas is also controlled in a defined manner and thus the energy level in the resonator even during the breaks. This means that when the laser is switched on again, pulses of the same level as in the previous pulse sequence can be emitted immediately. The resonator can be controlled with the high-frequency pump voltage during the jump phases in different variants. It is thus possible to continuously modulate the high-frequency voltage during these jump phases. But it is also possible for a defined switch-off time at the beginning and / or at the end of the
Sprungphasen hin die RF-Leistung ganz abzuschalten oder ganz einzuschalten und nur in der restlichen Zeit eine modulierte Spannung mit einem vorgegebenen Tastverhaltnis anzulegen.Jump phases towards completely switching off or switching on the RF power and only applying a modulated voltage with a predefined duty cycle in the remaining time.
Weiterhin kann das erfindungsgemaße Verfahren dahingehend erweitert werden, daß nicht nur wahrend der Sprungphasen bei der Bearbeitung eines bestimmten Bearbeitungsfeldes, sondern auch bei längeren Pausen, etwa beim Wechsel von einem Bearbeitungsfeld zu einem nächsten oder bei einem Bereitschafts- Betriebszustand des Systems, die Modulation der Hochfrequenzspannung am Resonator weitergeführt wird. Für die Ermittlung des notwendigen Tastverhaltnisses bei der erfindungsgemaßen Modulation sind verschiedene Kriterien, insbesondere die Eigenschaften des speziellen Laserresonators zu berücksichtigen. Vorzugsweise wird dieses Tastverhaltnis deshalb experimentell ermittelt, indem beispielsweise bei unterschiedlichen Puls-Pausen-Verhaltnissen der Hochfrequenzspannung mit abgeschaltetem Laser Probelocher gebohrt und auf ihre Lochqualitat untersucht werden. Es ist aber auch möglich, das in dem Resonator herrschende Energieniveau durch Abgabe von Probepulsen des Lasers und Messung der Pulshohen zu ermitteln. Die Pulshohen können dabei mittels einer Photodiode oder dergleichen gemessen werden.Furthermore, the method according to the invention can be expanded in such a way that the modulation of the high-frequency voltage not only during the jump phases when processing a specific processing field, but also during longer breaks, for example when changing from one processing field to a next or when the system is in a standby operating state is continued at the resonator. Various criteria, in particular the properties of the special laser resonator, must be taken into account in order to determine the necessary duty cycle in the modulation according to the invention. This duty cycle is therefore preferably determined experimentally by, for example, drilling at different pulse-pause ratios of the high-frequency voltage with the laser switched off, and examining the quality of the holes. However, it is also possible to determine the energy level prevailing in the resonator by emitting test pulses from the laser and measuring the pulse heights. The pulse heights can be measured by means of a photodiode or the like.
Die Erfindung wird nachfolgend an Ausfuhrungsbeispielen an- hand der Zeichnung naher erläutert. Es zeigtThe invention is explained in more detail below using exemplary embodiments with reference to the drawing. It shows
Figur 1 eine schematische Darstellung eines Gaslaser-Systems für die Anwendung des erfindungsgemaßen Verfahrens,FIG. 1 shows a schematic representation of a gas laser system for the application of the method according to the invention,
Figur 2 die verschiedenen, m dem Laserresonator wirksamen Signale zur Erzeugung von Laserpulsen,FIG. 2 shows the various signals effective for generating laser pulses in the laser resonator,
Figur 3 ein Zeitdiagramm mit den AnSteuerimpulsen für den La- serresonator n der Arbeitsphase und der Sprungphase bei einem herkömmlichen Verfahren, Figuren 4,5 und 6 entsprechende Zeitdiagramme mit den Ansteu- erimpulsen für den Laserresonator bei dem erfindungsgemaßen Verfahren in drei verschiedenen Varianten.3 shows a time diagram with the control pulses for the laser resonator in the working phase and the jump phase in a conventional method, FIGS. 4, 5 and 6 corresponding time diagrams with the control pulses for the laser resonator in the method according to the invention in three different variants.
Figur 1 zeigt ein Lasersystem für ein erfindungsgemaßes Verfahren. Dabei ist ein Resonator 1 mit einer mit einer Gasmi- schung, vorzugsweise mit CO?, gefüllten Kammer vorgesehen, an das über ein Elektrodensystem 2 eine Hochfrequenzspannung RF angelegt wird. Der Resonator 1 wird weiterhin über ein Kuhl- system 3 mit entsprechenden Kuhlmittelanschlussen gekühlt. Mittels eines Guteschalters 4 in Form einer elektrooptischen Modulatoranordnung, der über eine entsprechende Pulsansteuerung 5 mit Hochfrequenzspannung versorgt wird, werden mit Hilfe einer ebenfalls nur schematisch gezeigten Spiegelanord nung 6 Pulse über ein Fenster 7 in den Resonator 1 geschickt und dort über weitere Spiegelanordnungen 8 geleitet. Eine geschickte Anordnung der Spiegel auf kleinem Raum vergrößert die wirksame Lange des aktiven Resonators. Auf diese Weise werden Laserpulse LP erzeugt, die über ein Ausgangsfenster 9 aus dem Resonator sowie über eine Ablenkeinheit 10 mit beweglichen Spiegelanordnungen auf ein Werkstuck 11 gelenkt wird, um dort an den jeweiligen Arbeitspositionen dieses Werkstuck zu bearbeiten, beispielsweise Locher zu bohren. Das Werkstuck 11 ist auf einem verstellbaren Tisch 12 angeordnet, wodurch jeweils bestimmte Bearbeitungsfelder des Werkstucks in den Bereich des Laserstrahls gebracht werden können. Sowohl der Tisch 12 als auch die Ablenkeinheit 10 werden durch ein Positioniersystem 13 gesteuert, das seinerseits von einer zentra- len Steuereinheit 14 gesteuert wird. Diese zentrale Steuereinheit 14 koordiniert auch die Hochfrequenzspannung RF an dem Resonator und die Erzeugung der Pulse über den Guteschalter 4 bzw. dessen Ansteuerung 5. Dieses System gemäß Figur 1 ist bekannt und mit seinen wesentlichen Elementen in WO 02/082596 A2 beschrieben.Figure 1 shows a laser system for a method according to the invention. Here, a resonator 1 with a gas mixture, preferably with CO ? , filled chamber is provided, to which a high-frequency voltage RF is applied via an electrode system 2. The resonator 1 is also cooled via a cooling system 3 with corresponding coolant connections. By means of a good switch 4 in the form of an electro-optical modulator arrangement, which is supplied with high-frequency voltage via a corresponding pulse control 5, a mirror arrangement, likewise only shown schematically, is used 6 pulses sent through a window 7 into the resonator 1 and passed there via further mirror arrangements 8. A clever arrangement of the mirrors in a small space increases the effective length of the active resonator. In this way, laser pulses LP are generated, which are directed via an output window 9 out of the resonator and via a deflection unit 10 with movable mirror arrangements onto a workpiece 11 in order to machine this workpiece there, for example to drill holes, at the respective working positions. The workpiece 11 is arranged on an adjustable table 12, whereby certain machining fields of the workpiece can be brought into the area of the laser beam. Both the table 12 and the deflection unit 10 are controlled by a positioning system 13, which in turn is controlled by a central control unit 14. This central control unit 14 also coordinates the high-frequency voltage RF at the resonator and the generation of the pulses via the good switch 4 or its control 5. This system according to FIG. 1 is known and is described with its essential elements in WO 02/082596 A2.
Figur 2 zeigt das Pulsdiagramm eines Systems gemäß Figur 1 in herkömmlicher Betriebswe se. Zum Starten einer Pulsfolge w rd zum Zeitpunkt tbl von der Steuereinrichtung 14 die Hochfre- quenzspannung RF an den Resonator angelegt, der sich für die Dauer dieser anliegenden Spannung im Erregungszustand befindet. Wenn dann von der Steuereinrichtung 5 Triggerpulse TP an den Guteschalter 4 angelegt werden, gibt der Resonator eine entsprechende Pulsfolge von Laserpulsen LP ab.FIG. 2 shows the pulse diagram of a system according to FIG. 1 in a conventional operating mode. To start a pulse sequence, the control device 14 applies the high-frequency voltage RF to the resonator at time tbl, which is in the excitation state for the duration of this applied voltage. If the control device 5 then applies trigger pulses TP to the good switch 4, the resonator emits a corresponding pulse sequence of laser pulses LP.
Figur 3 zeigt eine entsprechende Pulsfolge beim Bohren von Lochern in unterschiedlichen Abstanden auf einer Leiterplatte (in den Figuren 3 bis 6 sind alle Signale beispielsweise low aktiv dargestellt; naturlich wäre auch eine Darstellung mit high active möglich) . Gezeigt ist ein Beispiel, bei dem einzelne Arbeitsphasen APH1, APH2 und APH3 jeweils zum Bohren eines Loches dienen, wahrend zwischen den Arbeitsphasen je weils Sprungphasen SPHl und SPH2 den Sprung der Strahlablenkung von dem ersten Loch zum zweiten usw. ermöglichen. Wie aus Figur 3 zu sehen ist, sind die Sprungphasen unterschiedlich lang, da die Abstände der zu bohrenden Locher unter- schiedlich groß sind. In der Praxis geht es dabei beispielsweise um Abstände in der Größenordnung von 200 μm bis 50 mm, wobei ein Sprung etwa 200 μs bis 300 ms dauert. Wie aus Figur 3 weiter zu ersehen ist, ist wahrend der Sprungphasen SPHl und SPH2 nicht nur der Laserstrahl selbst (durch die fehlen- den Triggerimpulse) abgeschaltet, sondern auch die Hochfrequenzspannung RF am Resonator ist abgeschaltet. Dadurch ergeben sich unterschiedliche Abkühlungen und ein unterschiedliches Absinken des Energieniveaus in dem Resonator entsprechend den unterschiedlich langen Sprungphasen.Figure 3 shows a corresponding pulse sequence when drilling holes at different distances on a circuit board (in Figures 3 to 6, all signals are shown, for example, low active; of course, a representation with high active would also be possible). An example is shown in which individual work phases APH1, APH2 and APH3 each serve to drill a hole, while between the work phases each because jump phases SPH1 and SPH2 enable the beam deflection to jump from the first hole to the second, etc. As can be seen from FIG. 3, the jump phases are of different lengths since the distances between the holes to be drilled are different. In practice, this involves, for example, distances of the order of 200 μm to 50 mm, with a jump taking about 200 μs to 300 ms. As can also be seen from FIG. 3, not only is the laser beam itself switched off (due to the missing trigger pulses) during the jump phases SPH1 and SPH2, but also the high-frequency voltage RF at the resonator is switched off. This results in different cooling and a different decrease in the energy level in the resonator in accordance with the different long jump phases.
Figur 4 zeigt ein erstes Beispiel für eine erfindungsgemaße Betriebsweise. Hier wird in den Sprungphasen wie zuvor beim herkömmlichen Verfahren die Triggerung des Lasers über dem Guteschalter deaktiviert. Jedoch wird die RF- (Hochfrequenz) - Leistung jeweils über die gesamte Sprungphase mit einem vorgegebenen Tastverhaltnis von tl zu t2 intermittierend angelegt, so daß das Gesamtverhaltnis der Sprungphasen SPH zu den Arbeitsphasen APH ("RF-Leistung OFF" zu "RF-Leistung ON") ausgeglichen ist. Hierdurch wird die im Vergleich zu der Ar- beitsphase APH größere Spannungsphase SPH kompensiert, und es wird ein ausgeglichenes Energieniveau erreicht.FIG. 4 shows a first example of an operating mode according to the invention. Here the triggering of the laser is deactivated via the good switch in the jump phases as before in the conventional method. However, the RF (radio frequency) power is applied intermittently over the entire jump phase with a predetermined duty cycle from tl to t2, so that the overall ratio of the jump phases SPH to the working phases APH ("RF power OFF" to "RF power ON ") is balanced. This compensates for the voltage phase SPH, which is larger in comparison to the working phase APH, and a balanced energy level is achieved.
Figur 5 zeigt eine etwas abgewandelte Ausfuhrungsform bei gleichen Langen der Arbeitsphasen APH1 bis APH3 und der zwi- schenliegenden Sprungphasen SPHl und SPH2 wie bei dem vorhergehenden Beispiel. In diesem Fall wird die intermittierende Modulation der RF-Leistung jeweils gleich zu Beginn der Sprungphase gestaltet. Dann jedoch wird für eine vorgegebene Pausenzeit PZ mit der Lange t3 die Erregung des Resonators bis zum Beginn der nächsten Arbeitsphase dauerhaft ab- oder angeschaltet . Wie in Figur 6 gezeigt ist, ist es in einer anderen Variante möglich, die Sprungphase SPHl bzw. SPH2 jeweils mit einer definierten Pausenzeit PZ der Lange t3 oder auch unterschiedlicher Langen zu beginnen und dann bis zum Beginn der nächsten Arbeitsphase die intermittierende RF-Leistung an den Resonator anzulegen. Genauso ist es möglich, die Varianten der Figuren 5 und 6 zu kombinieren, also jeweils zu Beginn und zum Ende einer Sprungphase eine Pausenzeit einzulegen und dazwischen die intermittierende RF-Leistung am Resonator so anzu- legen, daß jedenfalls zum Beginn der nächsten Arbeitsphase die Temperatur bzw. das Energieniveau in dem Resonator den Verhaltnissen bei der vorhergehenden Arbeitsphase entspricht. Die Laserpulsfolgen LPF1, LPF2 und LPF3 und daraus resultierend die Arbeitsphasen APH1, APH2 und APH3 können auch unter- schiedlich lang sein. FIG. 5 shows a somewhat modified embodiment with the same lengths of the working phases APH1 to APH3 and the intermediate jumping phases SPH1 and SPH2 as in the previous example. In this case, the intermittent modulation of the RF power is designed right at the beginning of the jump phase. Then, however, the excitation of the resonator is permanently switched off or on for a predetermined pause time PZ with the length t3 until the start of the next working phase. As shown in FIG. 6, in another variant it is possible to start the jump phase SPH1 or SPH2 with a defined pause time PZ of length t3 or different lengths and then to start the intermittent RF power until the start of the next work phase put on the resonator. It is also possible to combine the variants of FIGS. 5 and 6, ie to take a break at the beginning and at the end of a jump phase and to apply the intermittent RF power between the resonators in such a way that the temperature at least at the beginning of the next working phase or the energy level in the resonator corresponds to the conditions in the previous work phase. The laser pulse sequences LPF1, LPF2 and LPF3 and the resulting work phases APH1, APH2 and APH3 can also be of different lengths.

Claims

Patentansprüche claims
1. Verfahren zum Betrieb eines Gaslasersystems zur Bearbeitung von Substraten mit einem Gaslaser, insbesondere einem Cθ2-Laser, bei dem in einem gasgefullten Laserresonator (1) , an welchem eine Hochfrequenzspannung (RF) zur Erzeugung einer vorgegebenen Pumpleistung wahrend einer jeweiligen Arbeitsphase (APH) anliegt, und in welchem mittels eines Guteschalters (4) ein gepulster Laserstrahl (LP) mit einer vorgegebe- nen Wiederholfrequenz erzeugt wird, der durch eine Ablenkeinheit (10) jeweils zu einer Bearbeitungsposition gelenkt wird, dort während einer Arbeitsphase (APH1, APH2, APH3) eine vorgegebene Anzahl von Pulsen (LPF1, LPF2, LPF3) abgibt und dann mittels der Ablenkeinheit (10) in einer Sprungphase (SPHl, SPH2) zu einer nächsten Bearbeitungsposition gelenkt wird, wobei jeweils wahrend der Sprungphase von einer Bearbeitungsposition zu einer nächsten der Laserstrahl (LP) abgeschaltet wird und keine Pulse nach außen abgibt, d a d u r c h g e k e n n z e i c h n e t , daß die Hoch- frequenz-Pumpenergie (RF) während der Sprungphasen1. A method for operating a gas laser system for processing substrates with a gas laser, in particular a CO 2 laser, in which in a gas-filled laser resonator (1), at which a high-frequency voltage (RF) for generating a predetermined pumping power during a respective working phase (APH ) is applied, and in which a pulsed laser beam (LP) with a predetermined repetition frequency is generated by means of a good switch (4), which is deflected by a deflection unit (10) to a processing position, there during a work phase (APH1, APH2, APH3) emits a predetermined number of pulses (LPF1, LPF2, LPF3) and is then steered by means of the deflection unit (10) in a jump phase (SPH1, SPH2) to a next processing position, whereby during the jumping phase from one processing position to another Laser beam (LP) is switched off and emits no pulses to the outside, characterized in that the high-frequency pump energy (RF) during the jump phases
(SPH1,SPH2) intermittierend an den Laserresonator (1) derart angelegt wird, daß das Energieniveau in dem Resonator auf annähernd der gleichen Hohe gehalten wi d wie wahrend der Arbeitsphasen (APH1, APH2, APH3) .(SPH1, SPH2) is intermittently applied to the laser resonator (1) in such a way that the energy level in the resonator is kept at approximately the same level as during the working phases (APH1, APH2, APH3).
2. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t , daß jeweils wahrend der gesamten Sprungphase (SPH1,SPH2) des Laserstrahls die Hoch requenz-Pumpenergie (RF) in einem vorgegebenen Puls/Pausen-Verhaltnis (tl,t2) moduliert wird.2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the high-frequency pump energy (RF) is modulated in a predetermined pulse / pause ratio (tl, t2) during the entire jump phase (SPH1, SPH2) of the laser beam.
3. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t , daß nach einer Arbeitsphase (APH1, APH2, APH3) jeweils die Hochfrequenz- Pumpspannung (RF) für ein bestimmtes Zeitintervall mit einem vorgegebenen Puls/Pausen-Verhaltnis (tl,t2) moduliert und dann für eine vorgegebene Pausenzeit (PZ) bis zum Beginn der nächsten Arbeitsphase (APH2,APH3) abgeschaltet oder definiert angeschaltet wird.3. The method according to claim 1, characterized in that after a working phase (APH1, APH2, APH3) each the high-frequency pump voltage (RF) for a certain time interval with a predetermined pulse / pause ratio (tl, t2) and then modulated for one predetermined pause time (PZ) until the start of the next working phase (APH2, APH3) is switched off or switched on in a defined manner.
4. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t , daß nach einer Bearbeitungsphase (APH1, APH2, APH3) die Hochfrequenz- Pumpspannung (RF) zunächst für eine vorgegebene Pausenzeit (PZ) abgeschaltet und danach in einem bestimmten Puls/Pausen- Verhaltnis (tl,t2) moduliert wird.4. The method according to claim 1, characterized in that after a processing phase (APH1, APH2, APH3) the high-frequency pump voltage (RF) is first switched off for a predetermined pause time (PZ) and then in a certain pulse / pause ratio (tl, t2 ) is modulated.
5. Verfahren nach Anspruch 1, d a d u r c h g e k e n n z e i c h n e t , daß die Hochfrequenz-Pumpspannung (RF) sowohl zu Beginn als auch zum Ende einer Sprungphase (SPH1,SPH2) für eine bestimmte Pausenzeit (PZ) ab- oder angeschaltet und wahrend der restlichen Sprungphase in einem vorgegebenen Puls/Pausen-Verhaltnis moduliert wird.5. The method according to claim 1, characterized in that the high-frequency pump voltage (RF) both at the beginning and at the end of a jump phase (SPH1, SPH2) switched off or on for a certain pause time (PZ) and during the remaining jump phase in a predetermined Pulse / pause ratio is modulated.
6. Verfahren nach einem der Ansprüche 1 bis 5, d a d u r c h g e k e n n z e i c h n e t , daß die Hochfrequenz-Pumpspannung (RF) auch wahrend einer Bereitschafts- Betriebsart des Lasersystems intermittierend angelegt wird.6. The method according to any one of claims 1 to 5, so that the high-frequency pump voltage (RF) is also applied intermittently during a standby mode of operation of the laser system.
7. Verfahren nach einem der Ansprüche 1 bis 6, d a d u r c h g e k e n n z e i c h n e t , daß zur Einstellung des Puls/Pausen-Verhaltnisses (t2/tl) für die intermittierende Hochfrequenz-Pumpleistung das Energieniveau in dem Resonator (1) durch Bohren von Probelochern und anschließender Prüfung der Lochqualitat ermittelt wird.7. The method according to any one of claims 1 to 6, characterized in that for adjusting the pulse / pause ratio (t2 / tl) for the intermittent high-frequency pumping power, the energy level in the resonator (1) by drilling test holes and then testing the hole quality is determined.
8. Verfahren nach einem der Ansprüche 1 bis 6, d a d u r c h g e k e n n z e i c h n e t , daß zur Einstellung des Puls/Pausen-Verhaltnisses (t2/tl) für die intermittierende Hochfrequenz-Pumpleistung das Energieniveau in dem Resonator (1) durch Abgabe von Probepulsen und durch Messung der Pulshohe ermittelt wird. 8. The method according to any one of claims 1 to 6, characterized in that for adjusting the pulse / pause ratio (t2 / tl) for the intermittent high-frequency pumping power, the energy level in the resonator (1) by emitting test pulses and by measuring the pulse height is determined.
9. Verfahren nach Anspruch 8, d a d u r c h g e k e n n z e i c h n e t , daß die Pulshohen mittels einer Photodiode gemessen werden. 9. The method according to claim 8, d a d u r c h g e k e n n z e i c h n e t that the pulse heights are measured by means of a photodiode.
PCT/EP2004/050555 2003-09-30 2004-04-16 Method for operating a gas laser system WO2005032758A1 (en)

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