WO2013079450A1

WO2013079450A1 - Laser machining system

Info

Publication number: WO2013079450A1
Application number: PCT/EP2012/073642
Authority: WO
Inventors: Tino Petsch; Frank Allenstein; Heiko BÄR; Martin Sachse
Original assignee: 3D-Micromac Ag
Priority date: 2011-11-28
Filing date: 2012-11-26
Publication date: 2013-06-06
Also published as: DE102011087181A1; DE102011087181B4

Abstract

A laser machining system (100) which can be used, for example, in a line production plant for producing printed electronic components on a band-like flexible substrate in a roll-to-roll method, has a housing (110), which can be closed off in a gas-tight manner and encloses a process chamber (112), at least one substrate holding device (120) which is arranged in the process chamber and is set up to hold the substrate (115) for laser machining in a machining position within the process chamber, and a laser unit (140), fitted outside the housing, having an exit optical system (150) for emitting a laser beam that can be directed onto the substrate, wherein an optical window (170), which is transparent to the laser beam, for injecting the laser beam into the process chamber is provided, said optical window (170) separating the process chamber from the surroundings. The exit optical system (150) of the laser unit (140) is coupled in a mechanically rigid manner to the substrate holding device (120) and mechanically uncoupled from the housing (110).

Description

description

Laserbearbeitunqssvstem

BACKGROUND

The invention relates to a laser processing system according to the preamble of claim 1.

Laser processing systems of this type permit laser processing of substrates in a process chamber sealed off from the environment, e.g. under vacuum, negative pressure, overpressure and / or a defined protective gas atmosphere. A gas-tight lockable housing encloses a process chamber. Mounted in the process chamber is a substrate holding device configured to hold a substrate to be processed for laser processing in a processing position within the process chamber. The substrate may be, for example, a rigid glass substrate or metal substrate or may be a flexible substrate, e.g. a portion of a tape-shaped flexible substrate used in the manufacture of printed electronics.

Outside the housing, a laser unit is mounted with an exit optics, which emits a, usually focused on the substrate laser beam. This can be directed, for example, by means of a scanning device successively along a path with a defined course over the region of the substrate to be processed in order to process it by means of the locally irradiated laser radiation. The laser beam is thereby coupled into the process chamber through an optical window transparent to the laser radiation. The optical window separates the process chamber from the environment in which the laser unit is mounted. Such a laser processing system can be used, for example, as a processing station in a belt manufacturing line for producing printed electronic components on a belt-shaped flexible substrate in a roll-to-roll process. However, it is also possible to use a laser processing system in the context of batch processes or inline processes or as a stand-alone system.

A problem with such laser processing systems is to position the substrate to be processed under different operating conditions as accurately as possible in the processing position and to irradiate the laser beam as accurately as possible and with defined beam quality to the particular surface areas to be processed under all operating conditions. These problems become more critical the smaller the structures to be created or changed on the substrate become.

TASK AND SOLUTION

Against this background, the invention has for its object to provide a laser processing system of the type mentioned, which ensures an exact processing of positioned in a process chamber substrates under different operating conditions. To achieve this object, the invention provides a laser processing system having the features of claim 1. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

In a laser processing system according to the invention, the exit optics of the laser unit with the substrate holding device is mechanically rigidly coupled and mechanically from the housing of the process chamber decoupled. A mechanical decoupling is given in particular if during a relative movement of the mechanically decoupled elements between them no or only very small forces can be transmitted, so that the decoupled elements can move largely independently of each other and the movement of one of the elements does not affect the state of motion or the position of the other element to a practically relevant extent. It can thereby be achieved that the focus area of the laser beam irradiated for processing into the process chamber is always correctly positioned independently of any movements of the housing walls with respect to the substrate held by the substrate holding device. Due to the rigid mechanical coupling between the laser unit or its exit optics and the substrate holding device, the spatial relationship between these two devices within the given by the mechanical coupling tolerances is always maintained, even if the housing or wall elements of the housing relative to the laser unit and / or move to the substrate unit

If the radiation source (laser unit) is placed outside the process chamber, e.g. the problem arises that the position of the substrate or the substrate holding device with respect to the position of the radiation source (laser unit) and its external components changes when the pressure in the process chamber changes with respect to the external pressure (atmospheric pressure) because thereby Forces can result, which can deform the housing walls of the process chamber and thus affect chamber components, such as may have the substrate holding device. The invention avoids the emergence of such problems by design measures.

The mechanical decoupling between the housing of the process chamber and the laser unit or its exit optics provides simultaneously that relative movements between the housing walls and the laser unit can not affect the relative spatial positioning of the laser unit to the substrate holding device. A laser unit normally has a base unit to which optical components of the laser unit are mounted in the required geometric arrangement with each other. Typically, a base unit will have a granite block or block of another material with extremely low coefficients of thermal expansion. Metallic frame elements can be mounted on this block. The substrate holding device also typically has a base unit on which one or more substrate holding members formed for contact with the substrate are mounted. The base may, for example, have a torsion-resistant construction with steel plates and / or steel profiles.

In one embodiment, the base unit of the laser unit functions as a support for the base unit of the substrate holding device so that it does not require a supporting connection with an element of the housing. The substrate holding device may be e.g. be suspended above the housing bottom.

In one embodiment, a base unit of the laser unit is mechanically rigidly connected to a base unit of the substrate holding device via at least one connecting element, wherein the connecting element is guided through a passage opening in a wall element of the housing such that an all-round radial connection between the connecting element and the edge of the passage opening Distance, for example in the form of an annular gap exists. Thus, the base of the laser unit can function as a support for the base unit of the substrate holding device, so that it does not require a supporting connection with an element of the housing. Because the connecting element passes through the wall element of the housing in the area of the passage opening without contact, movements of the wall element can occur do not interfere with the relative positioning of the laser unit and the substrate holding device, so that a mechanical decoupling can be realized. In some embodiments, a plurality of connecting elements, for example three or four connecting elements, are provided between the base units of the laser unit and the substrate holding device in order to ensure a particularly rigid, stable mounting of the substrate holding device on the laser unit. Each of the connecting elements may be guided in a corresponding manner without contact by an associated passage opening. The connecting elements are designed in some embodiments as telescopic rods, ie as connecting elements that are adjustable in length. As a result, an exact alignment of the substrate holder with respect to the laser unit during assembly and possible maintenance or retooling is possible.

In order to enable a hermetic sealing of the process chamber also in the region of the through openings which are penetrated by connecting elements, corresponding sealing devices are preferably provided. A sealing device can be designed so that there are no sealing elements in the gap formed between the connecting element and the edge of the associated through-opening, so that in this area even with relative transverse movements or longitudinal movements no forces are transmitted directly between the connecting element and wall element. Sealing elements are preferably mounted outside the region of the passage opening.

In some embodiments, a sealing device for sealing the passage opening has a gas-impermeable, optionally vacuum-resistant bellows enclosing the connecting element, which can be designed, for example, as a bellows or bellows. The bellows can on the one hand with the interposition of a first sealing element the outside of the wall element and on the other hand with an axial distance to rest with the interposition of a second sealing element on a fixedly connected to the connecting element flange. In this arrangement, sealing surfaces may be formed by axial end faces of the bellows or of the wall element and of the flange element, so that a pure axial sealing device is provided. Due to the flexibility of the bellows in the axial direction and in the lateral direction, longitudinal and transverse movements of the connecting element in the passage opening are possible, without there being any significant effect on the housing.

In some embodiments, special measures are taken in the region of the optical window, which ensure that the laser beam can be optically coupled exactly into the process chamber, without any relative movements between the laser unit and the housing to influence the beam path of the laser beam. For this purpose, in one embodiment in a housing-fixed wall element of the housing, a passage opening associated with the optical window is provided. However, the optical window is not inserted in this through-opening, but accommodated in a separate from the wall element holder unit, which is connected to the wall element via a flexible gas-tight connection means. The mounting unit, in turn, is mechanically rigidly connected to the laser unit or its exit optics, so that their relative spatial relationship is fixed and also remains when the wall element having the passage opening moves relative to the laser unit. The flexible gas-tight connection device compensates for a possible relative movement between the holder unit and the wall element and at the same time decouples the housing mechanically from the laser unit.

Preferably, the connecting device has at least one gas-tight, optionally vacuum-resistant bellows. Such a bellows, the For example, can be designed as a bellows or bellows made of metal or plastic, can compensate for relative movements between the housing and the laser unit and simultaneously decouple these elements mechanically.

In the processing of substrates by means of high-energy laser radiation, by evaporation or melting of materials, for example, machining products are produced which, on the one hand, impair the machining process and, on the other hand, can also cause problems on the processed substrate. In order to prevent laser processing machining products from re-depositing on the processed substrate, in preferred embodiments, the substrate holding device is constructed such that the surface of a substrate held in the processing position is vertically or substantially vertically aligned. The term "essentially vertical" here means, in particular, that an angle between the surface of the substrate and the vertical direction should not be greater than 30 ° or 20 ° or 10 ° and / or in some other way optionally athermically detached substrate material can not fall back onto the processed substrate, thereby supporting the production of cleaner, low-defect components.

When processing materials with concentrated electromagnetic radiation, such as laser radiation, especially under negative pressure, a plasma cloud often forms in front of the substrate surface. In addition to gases, this plasma cloud contains partly ionized particles, which may be present in the solid and liquid state. Components that are located in the area of the plasma cloud can be severely impaired in their function by "coating" the material, especially solids such as metal particles, in particular optics such as optical entrance windows or focusing lenses, or by erosion on their surface Due to the arrangement of the laser unit Outside the process chamber, the components of the laser unit are protected. However, a problem that is possible with generic laser processing systems consists in the fact that the inside of the optical window can become increasingly polluted and / or wear out as a result of increasing operating time through processing products. As a result, the coupling of the laser beam would be increasingly affected.

One way to deal with this problem is to design the optical window as a replaceable element so that it can either be easily cleaned after installation or replaced with another clean optical easy window. Preferably, however, measures are taken to avoid a disadvantageous for operation pollution of the optical window or to reduce to an uncritical extent. In some embodiments, for this purpose, the exit optics of the laser unit is aligned obliquely with respect to the substrate holding device such that an optical axis of the exit optics encloses an acute angle with a normal direction of the surface of a substrate held by the substrate holding device. The acute angle may for example be between 10 ° and 50 °, in particular in the range between 20 ° and 35 °, for example at about 25 °. This measure takes into account that a plasma cloud with processing residues can form above the processed substrate surface during laser processing, the particle current density of the processing residues in the normal direction of the substrate surface being particularly high and decreasing greatly towards the sides. The oblique arrangement can thus be achieved that, starting from the substrate, only relatively few machining residue particles per unit of time are directed in the direction of the optical window, whereby the tendency to fouling is greatly reduced. On the other hand, the radiation is still steep enough, so that an exact positioning of the focus area on the substrate is possible. This measure can be used advantageously regardless of the features of the claimed invention in other laser processing systems. In some embodiments, alternatively or additionally, a separate window protection device is provided for protecting the window from contamination by laser processing processing products, the window protection device having at least one laser beam transparent protective element disposed between the substrate and the optical window. As a result, those processing products that move from the substrate in the direction of the optical window can be absorbed by the transparent protective element and thus not pollute the optical window. Preferably, a window without a tool (ie without the aid of a tool) replaceable window protection device is provided, whereby maintenance is simplified.

In one embodiment, the transparent protective element is aligned obliquely with respect to an irradiation direction of the laser beam such that laser light reflected by the protective element is not reflected in the exit optics of the laser unit. On the other hand, in order to avoid that the coupled laser beam is deflected by the transparent protective element on the way to the substrate in a poorly controllable manner, it has proven advantageous if the transparent protective element is placed at a relatively small angle obliquely to the direction of irradiation of the laser beam, so that it is irradiated approximately vertically. In particular, an angle between a normal direction of the transparent protective element and the irradiation direction or the optical axis of the output optics may be less than 15 ° and, for example, between 3 ° and 10 °, for example at approximately 4 °. Interchangeable transparent protective elements can be provided, for example in the form of plates made of glass or another material transparent to the laser radiation. In preferred embodiments, the transparent protective element is formed by a section of a flexible film strip, wherein the window protection device preferably has a first roll with a supply of fresh foil strip and a second roll for winding used foil strip, wherein a foil section cantilevered between the rolls separates the foil section Protective element forms. By a winding mechanism can be tracked continuously or discontinuously (intermittently) fresh foil tape, so that at any time a sufficiently transparent film section is available as a protective element. The current contamination of the transparent protective element can be detected by a suitable detection device and a corresponding signal for controlling the winding device can be processed in order to control the feed of the film strip in dependence on the strength of the pollution can.

Such a window protection device can also be advantageously used in other laser processing systems, regardless of the features of the claimed invention.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Can represent versions. BRIEF DESCRIPTION OF THE DRAWING FIGURES

Fig. 1 shows a schematic partial view of a laser processing system according to an embodiment of the invention; FIG. 2 shows an oblique perspective view of a substrate holding device fixedly connected to the base of the laser unit and wall elements of the housing of the process chamber therebetween; FIG.

FIG. 3 shows a detail view of a through opening, which is penetrated by a connecting element and sealed by an axial sealing device, in a wall element of the housing; FIG. and

Fig. 4 shows an oblique perspective view of the surroundings of the optical window.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a schematic partial view of a laser processing system 100 according to an embodiment of the invention. The laser processing system is designed so that it can be used in a strip production line for the production of printed electronic components on strip-shaped flexible substrates in a roll-to-roll process. Laser processing is used here as a sub-process in the production of flexible CIS / CIGS thin-film solar cells, but can be used, for example. also in the production or structuring of organic light emitting diodes (OLED) or other printed electronic or electrical components, such as transistors, sensors or printed batteries, are used.

One feature of printed electrical or electronic components is the use of flexible, ie flexible substrate films which offer the possibility of roll-to-roll processing. In such a process, a thin plastic film or metal foil on the input side of a process line is fed from a roll into the process line. In the process line, one or more coating operations for depositing functional layers on the substrate film and structuring operations take place in different processing stations. The finished film can then be rolled up again or cut into the desired shape for further use. In this way, electronic components can be produced with relatively low production costs, on the other hand extremely lightweight and mechanically flexible components can be produced.

In the exemplary production of thin-film solar cells in a roll-to-roll process, the flexible carrier material (substrate) is first coated with layers of electrically conductive or semiconductive materials. These layers are usually only a few micrometers thick and are selectively removed or irradiated by laser irradiation with different wavelengths from the infrared range (IR), the visible range (VIS) or the ultraviolet range (UV) in the process steps P1, P2 and P3 of the overall process Slices separated laterally. For example, focused laser beams with a wavelength of 1030 nm or 515 nm are used. Typical line widths in the removal with focused laser beam are in the range of a few micrometers, for example between 20 μm and 50 μm. Write speeds up to several thousand mm / s can be achieved with high-performance laser units. An exact positioning of the focus area of the laser beam along the desired path is of great importance for the quality of the finished products.

The laser processing can take place in the laser processing system under vacuum or a defined gas atmosphere at negative pressure or overpressure (relative to the environment) in a hermetically sealable and optionally evacuatable process chamber. For this purpose, the laser processing system 100 has a pressure-resistant, multi-part design. tes housing 1 10, which hermetically encloses a evacuated by means of a pump process chamber 1 12, ie gas-tight.

In the interior of the housing, that is to say in the process chamber, at least one substrate holding device 120 is arranged, which in operation holds the substrate to be processed in a processing position suitable for the laser processing within the process chamber. In the illustrated example case, two substrate-holding devices 120, 120 'arranged mirror-symmetrically to one another and mechanically coupled to one another, are provided in an essentially identical manner, in order to enable parallel processing of two substrate webs. The following description of the substrate holding device shown on the left also applies analogously to the other substrate holding device. In the roll-to-roll system, the substrate to be processed in each case is formed by a section of a film strip 15 coated in upstream sub-processes. The substrate film, whose length can be up to several 100 m or several 1000 m, is introduced via a loading chamber, not shown, from above into the process chamber 12, processed there in sections, and then discharged again via an unloading chamber, not shown.

During the laser processing, the respectively processed foil band section can rest in the area of the substrate holding device. It is also possible to run processes in which the film strip is moved during the laser processing in the web direction with a uniform or irregular web speed. In order to enable in each case a continuous supply and removal of film strip, between the loading chamber and the substrate holding device and between the substrate holding device and Ausladekammer be arranged film tape buffer, for example those with dancer rollers or other means to maintain a sufficient Strap tension. If there is enough space, free-hanging foil tape loops can form.

Arrangement, structure and function of the substrate holding device 120 can be seen particularly well in FIGS. 1 and 2. The substrate holding device 120 is arranged in the region of the side wall 1 14 of the housing shown on the left in FIG. 1 at a vertical distance from the bottom of the process chamber. The laser unit 140 assigned to the substrate holding device 120 is arranged outside the housing 110 on the side of the side wall 14 opposite the substrate holding device. The laser unit 140 stands on top of a rollable frame 180, in which the electronic components of the control of the laser unit and display units are housed in the form of screens. A corresponding second laser unit 140 'is placed on the opposite side outside the housing.

The substrate holding device 120 has a multi-part base 122, which has a plurality of steel plates that are bolted together. A vertical support plate 124 of the base carries vertically above one another a first roller 132 and below a second roller 134 which are each rotatable about horizontally oriented roller axis. The rollers serve as substrate holding elements. In operation, the substrate film 1 15 is under suitable belt tension on the cylindrical outer surfaces of the rollers, so that the position of the rollers and their orientation to each other exactly specify the processing position of each to be processed film section. The vertical support plate 124 is screwed to a below the rollers arranged horizontal support plate 126 and other plates. The base may have further elements for stiffening.

A base 148 of the laser unit 140 has a solid granite block 142, on the horizontal, planar upper side of which the optical components (not shown) of the laser unit (eg resonator, deflector) are located. Mirrors, prisms, lenses, etc.). The granite block 142 is held by a torsion-resistant support frame having an attached laterally on the granite block vertical support plate 144 and acting on the underside of the support plate angled supports.

The coupled out of the resonator of the laser unit laser radiation is formed by suitable optical assemblies and optionally homogenized and occurs after passing through an exit optics 150 as laser beam 155 with high beam quality from the laser unit in the direction of the substrate. The coupling-out optical system 150 is fastened to a carrier plate screwed to the base and comprises a scanner system controllable via the control unit of the laser unit in order to successively direct the laser beam to different processing points on the surface of the stationary substrate. The solid angle range which can be scanned by the laser beam is shown by dashed lines in FIG. The main direction of irradiation is defined by the optical axis of the exit optics 150. In this case, the laser beam is irradiated obliquely from above onto the vertically aligned substrate, the optical axis of the exit optics 150 enclosing an acute angle of approximately 30 ° with the normal direction of the substrate surface aligned vertically between the rollers.

The emerging from the exit optics laser beam is coupled through an optical window 170 into the process chamber. The transparent to the laser beam optical window separates the interior of the housing 1 10, so the process chamber 1 12, from the environment in which the laser unit is located.

A special feature of the laser processing system is that the substrate holding device 120 is not attached to a fixedly connected to the housing 1 10 and its bottom member, but rigidly connected via rigid connecting elements with the base 148 of the laser unit 140, so that they are used as a carrier for the substrate holding direction. By contrast, the substrate holding device 120 is largely mechanically decoupled from the housing 110 so that movements of the housing, for example vibrations or pressure-related displacements of housing walls, are not or not disturbing the relative positioning between the laser unit 140 and the substrate holding device 120 or the housing held thereon Substrate can affect. Some constructive measures contributing to this will be explained in more detail below. The rigid mechanical connection between the base 148 of the laser unit 140 and the base 122 of the substrate holding device 120 is provided by a group of four connecting elements, each designed as a telescopic bolt. The two lower connecting elements 161, 162 are fixed with their outer end to the vertical support plate 144, while the inner end located in the process chamber is bolted to a respective attached to the underside of the horizontal support plate 126 block of material. A pair of upper connecting members 163, 164 similarly connects the support plate 144 associated with the base of the laser unit to a support member which is bolted to an angle member of the base 122 of the substrate support means. The stable, partially cylindrical connecting elements extend parallel to each other horizontally and pierce through each circular through holes 1 18, which are provided in a vertical wall element 1 16 of the multi-part housing 1 10 of the process chamber.

The detailed illustration in FIG. 3 clearly shows how it is ensured in the embodiment that there is no mechanical coupling between the wall element 116 and the centrally extending connecting element 161 in the region of the passage opening 118 and, on the other hand, the passage opening nevertheless sealed against the environment. The connecting element 161 has in the range of 1 opening 18 a cylindrical cross-section with an outer diameter which is significantly smaller than the inner diameter of the cylindrical passage opening. This ensures that between the outer side of the connecting element and the inner edge of the passage opening in all radial directions a distance 1 19 remains, so that in the region of the passage opening an annular gap is formed. The distance 1 19 may be on the order of one or more millimeters and is generally dimensioned so that in the largest expected relative movement between the wall member 1 16 and the connecting element 161, a contact contact between these elements in the region of the passage opening is reliably avoided.

To seal the region of the through-opening against ingress of ambient atmosphere into the process chamber, an axial sealing device 165 is provided, which does not require any radially acting sealing elements and transfers virtually no mechanical forces between these elements even with relative transverse movements and / or longitudinal movements of the connecting element relative to the wall element. wearing. An essential element of the sealing device is a vacuum-tight metallic bellows 166, which may be formed, for example, as a bellows or bellows. A first flange section 167 adjoins the side of the housing and a second flange section 168 on the side facing the laser unit, at an axially or transversely folded or corrugated center section. The first flange portion 167 is pressed with the interposition of an annular small flange seal to the outside of the wall element, whereby this area is sealed. The opposite second flange portion 168 is pressed with the interposition of a second small flange seal on a fixedly attached to the connecting element flange 169, whereby this area is sealed. In this axial sealing device only axial end faces are provided as sealing surfaces. Longitudinal and transverse movements of the connecting rod relative to the wall element 1 16 are thereby possible without substantial force-transmitting reaction to the housing, wherein the central bellows portion serves as a compensation element.

A further stabilization of the position of the two substrate holding devices 120, 120 'in the laser processing system 100 is given by the fact that their base units are rigidly interconnected by connecting elements.

In other embodiments, the housing is associated with only a single laser unit. In addition to at least one laser unit, at least one further, non-laser processing unit may also be provided on or in the housing.

Another special feature is provided in the region of the optical window 170 and will now be explained in more detail with reference to FIG. 4. The optical window 170, which may be formed by a plate of glass or other solid-state material transparent to the laser radiation, is not gripped in the illustrated circular through-hole 172 in a wall member 144 of the housing, but in a separate one from the wall member Holder unit 179. This has a base plate 182 with a circular passage opening in which the optical window is located. On the inside, a mounting ring 184 is provided with a smaller inner diameter, which supports the optical window inwards (to the negative pressure side of the process chamber). The socket unit is arranged at a distance in front of the associated wall element 1 14 of the housing. The holder unit is connected to this wall element via a flexible, vacuum-tight connection device 185, which in the example is formed by a bellows or corrugated bellows of suitable inner diameter. The optical window is thereby movably mounted relative to the housing of the process chamber. The frame unit is rigidly connected to the base unit of the laser unit because the inclined base plate 182 is fixed to the base unit.

This arrangement offers several advantages. On the one hand, it is ensured by the flexible connection device 185 that the laser unit or its exit optics 150 is mechanically decoupled from the housing 110, so that any vibrations or other movements of the housing wall can not be transmitted to the laser unit. Any relative movements are compensated by the bellows portion of the connecting device. Furthermore, it is ensured that the optical window is always in fixed spatial relation to the exit optics 150 of the laser unit. This precludes the possibility that the optical effect of the plane plate on the passing laser beam during laser processing changes in an uncontrollable manner, which could for example lead to an uncontrollable temporary beam offset.

To protect the optical window 170 against contamination by processing products of the laser processing, a window protection device 190 is provided, which is explained in more detail in particular in connection with FIG. The window protection device has a transparent to the laser radiation protection element 192, which is formed by a portion of a transparent film, which is disposed between the processed substrate and the substrate holding device and the optical window. In the direction of the optical window thrown machining products are collected by the transparent protective element and thus can not reach the optical window.

The window protection device 190 comprises a cassette 195, which can be easily replaced without tools by means of tools and which can be fastened to a carrier plate, for example, which is located in the region of the passage opening 172 assigned to the window on the inside of the associated wall element. For example, at the be arranged parallel plate holding profiles, between which the cassette can be inserted. Inside the cassette is a first roller 196, is wound on the fresh, still unused foil tape. At a distance opposite an axially parallel rotating second roller 198 is provided, which can be rotated continuously or intermittently by means of a roller drive to wind used foil strip sections as needed and rewet fresh foil strip. Between the rollers, the film strip is guided over two cassette-fixed bar-shaped deflecting elements such that a freely stretched film strip section lies between the deflecting elements and forms the transparent protective element. The crack-resistant plastic film of the film strip is in the example about 50 μητι thick.

The housing of the cassette has on the laser unit facing the beam inlet side and the substrate holding device facing the beam exit side protection plates in a central, substantially rectangular recess which is dimensioned so that the rollers are each protected between the protective plates inside the winding cassette and the laser beam in all can be irradiated by the scanning device adjustable Durchstrahlrichtungen without shading by the cassette into the interior of the process chamber.

The rod-shaped deflecting elements are arranged relative to one another such that the self-supporting foil band section penetrated by the laser beam is oriented somewhat obliquely at an angle deviating from 90 ° to the optical axis (in FIG. 4 coaxial with the laser beam) of the exit optics, so that the protective element reflects Laser light can not be reflected back into the exit optics 150. The oblique angle between the optical axis and the normal direction of the stretched film section is about 5 °, inter alia, depends on the axial distance between the exit optics and the protective element and may also be greater or less than 5 °. In order to optimize the processing quality in roll-to-roll systems and to maximize process reliability, sensors can be installed in front of and behind the processing station in the process chamber, for example in the form of line scan cameras, which evaluate between original and possibly pre-processed ones Substrates used to process results and allowing adjustment of process parameters depending on the specification or deviation. This can be used, for example, for the exact alignment of new laser cutting lines to be introduced to already existing laser cutting lines or markings. This control mechanism thus allows the control of process parameters.

For monitoring the laser processing, a monitoring system with line scan cameras is provided in the embodiment, which are connected to a communicating with the control of the system evaluation. An upper line camera 175 is mounted in the area above the first roller 132 and a second line camera 176 in the area below the second roller 134 relative to the substrate holding device, that by the line scan cameras the machined top of the substrate across the entire width through the Line scan cameras can be detected. As a result, any errors in the output structures can be detected on the entry side and any possible deviations of the geometry of the laser structures generated from a desired desired geometry can be detected early on the output side so that, if necessary, laser parameters can be readjusted to ensure a stable process. The line scan cameras are each arranged in the exemplary embodiment on an adjustable rail, so that the depth of field can be adjusted as needed. This adjustment can be made from outside the pressure housing via a cardan shaft.

In the embodiments described so far, the relative spatial positioning of the substrate holder relative to the Fixed laser unit by the mechanically rigid coupling between these devices. As a result, exact focusing of the laser beam on the substrate is ensured for most process requirements occurring in practice at any time without separate control engineering effort.

There may be laser processing systems in which the relative position between the external beam unit (here laser unit) and the workpiece or the substrate in the pressure chamber is variable within a certain tolerance range. This can e.g. be the case in generic laser processing systems without rigid coupling between the laser unit and substrate holding device. It may also be that in laser processing systems with rigid coupling so high demands are placed on the positioning accuracy that additional measures to improve the positioning accuracy can be beneficial.

In particular, in such cases, a laser processing system may include a compensation system having means for determining a time-varying change in the relative position between the exit optics of the laser unit and the substrate holding means and for generating a position signal representing the relative position change, and means for controlling laser parameters Have position signal. These devices can be configured so that the laser beam always hits the substrate surface even with changing relative positioning with defined beam quality, eg with a largely constant beam cross section in the focus area. As a result, the processing result can be made largely independent of any relative position changes. A compensation of relative position changes is possible, for example, by the position change is determined dynamically or regularly. Such a determination is possible, for example, by measurement by means of laser interferometry or by means of another, preferably optical, range finding method. In this case, for example, a laser interferometer (or another distance measuring device) can be positioned in the pressure chamber or process chamber and fixedly connected to the substrate holding device (workpiece holder unit) and measured at a fixed point on the external radiation source or the laser unit through the optical window. It is also possible for a fixed measuring point to be located on the workpiece receiving unit (substrate holding device) in the pressure chamber (process chamber) and for a laser interferometer to be fixedly attached to the laser unit or one of its components, such as scanners. If a plurality of distance measuring units are provided, for example a plurality of laser interferometers, it is also possible to determine three-dimensional position changes and to process corresponding position signals for controlling the laser unit. In order to compensate for the effects of relative positional changes by means of the control, beam shaping components and / or beam deflection components, such as scanners or focusing lenses, can be modified in their effect by moving these components accordingly. With the scanner, a corresponding angle compensation of the individual mirrors can be effected. The embodiments show laser processing systems used as a processing station in a belt manufacturing line for producing printed electronic components on a belt-shaped flexible substrate in a roll-to-roll process. It is also possible to use a laser processing system in the context of batch processes or inline processes or as a stand-alone system. As an alternative to band-shaped substrates, it is also possible to process any other form of substrates or workpieces, for example round, polygonal, in particular rectangular, individual metal substrates, polygonal substrates. merwerkstoff or the like. If necessary, the substrate holding device can also be designed as a xyz-stage or as a turntable.

Claims

claims

1. A laser processing system (100), in particular for use in a strip production line for producing printed electronic components on a strip-shaped flexible substrate in a roll-to-roll method, comprising:

a gas-tight lockable housing (1 10) enclosing a process chamber (1 12),

a substrate holding device (120) arranged in the process chamber and configured to hold the substrate (1 15) for laser processing in a processing position within the process chamber, and

a laser unit (140) mounted outside the housing and having outlet optics (150) for emitting a laser beam which can be aligned with the substrate,

wherein a transparent to the laser beam optical window (170) is provided for coupling the laser beam into the process chamber, which separates the process chamber from the environment,

characterized,

the exit optics (150) of the laser unit (140) are mechanically rigidly coupled to the substrate holding device (120) and mechanically decoupled from the housing (110).

2. A laser processing system according to claim 1, characterized in that a base unit (148) of the laser unit acts as a support for a base unit (122) of the substrate holding means and that there is no supporting connection between the substrate holding means (120) and an element of the housing.

3. Laser processing system according to claim 1 or 2, characterized in that a base unit (148) of the laser unit with a base unit (122) of the substrate holding device via at least at least one connecting element (161, 162, 163) is mechanically rigidly connected, wherein the connecting element is guided in such a way through a through hole (1 18) in a wall element (1 16) of the housing, that between the connecting element (161) and the edge of the through hole an all-round radial distance (1 19) consists.

Laser processing system according to claim 3, characterized in that a plurality of connecting elements, in particular three or four connecting elements (161, 162, 163) are provided between the base units of the laser unit and the substrate holding device, wherein each of the connecting elements is guided through an associated passage opening, wherein the connecting elements are adjustable in particular with regard to their length.

Laser processing system according to claim 2 or 4, characterized in that a sealing device (165) for sealing the passage opening (1 18) is provided, wherein the sealing device preferably comprises a connecting element enclosing the gas-tight bellows, in particular a bellows o- the bellows.

Laser processing system according to claim 5, characterized in that the bellows on the one hand with the interposition of a first sealing element on the outside of the wall element (1 16) and on the other at an axial distance thereto with the interposition of a second sealing element on a fixedly connected to the connecting element (161) flange (168 ) is present.

Laser processing system according to one of the preceding claims, characterized in that in a housing-fixed wall element (1 14) of the housing, an optical window (170) is provided through passage opening (172) is provided, that the optical window in a separate from the wall element holder unit (179) is accommodated and that the socket unit with the wall element via a flexible gas-tight connection means (185) is connected, wherein the connecting means preferably a Has bellows.

Laser processing system according to claim 7, characterized in that the optical window (170) is rigidly coupled to the exit optics (150) of the laser unit.

Laser processing system according to one of the preceding claims, characterized in that the substrate holding device (120) is constructed such that the surface of a held in the processing position, the substrate (1 15) is vertically or substantially vertically aligned.

Laser processing system according to one of the preceding claims, characterized in that the exit optics of the laser unit (140) with respect to the substrate holding device (120) is aligned obliquely such that an optical axis of the exit optics with a normal direction of the surface of a held by the substrate holding device a substrate Angle includes, wherein the acute angle is preferably between 10 ° and 50 °, in particular in the range between 20 ° and 35 °.

Laser processing system according to one of the preceding claims, characterized by a window protection device (190) for protection of the optical window (170) against contamination by laser processing products, wherein the window protection device has at least one protective element (192) transparent to the laser beam, which is located between the substrate and the optical window is arranged, wherein the window protection device is preferably replaceable, in particular without the aid of a tool.

Laser processing system according to claim 1 1, characterized in that the protective element (192) is aligned obliquely with respect to an irradiation direction of the laser beam that reflected by the protective element laser light is not reflected in the exit optics (150) of the laser unit.

Laser processing system according to claim 1 1 or 12, characterized in that the transparent protective element is formed by a portion of a flexible film strip, wherein preferably the window protection device, a first roll (196) with a supply of fresh foil tape and a second roll (198) for winding used foil strip, wherein a self-supporting stretched between the rollers film web portion forms the transparent protective element (192).

Laser processing system according to the preamble of claim 1, in particular according to one of the preceding claims, characterized by a compensation system with a device for determining a relative position between the exit optics of the laser unit and the substrate holding device and for generating a position signal representing the relative position and with a device for controlling of laser parameters as a function of the position signal, these devices being configured such that the laser beam always strikes the substrate surface even with a changing relative position with defined beam quality, in particular with a largely constant beam cross section in the focus area.