DE102015116848A1 - Dielectric workpiece with a zone of defined strength and method for its production and its use - Google Patents

Dielectric workpiece with a zone of defined strength and method for its production and its use

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Publication number
DE102015116848A1
DE102015116848A1 DE102015116848.0A DE102015116848A DE102015116848A1 DE 102015116848 A1 DE102015116848 A1 DE 102015116848A1 DE 102015116848 A DE102015116848 A DE 102015116848A DE 102015116848 A1 DE102015116848 A1 DE 102015116848A1
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Germany
Prior art keywords
workpiece
cavities
zone
preferably
strength
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Pending
Application number
DE102015116848.0A
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German (de)
Inventor
Florian Maurer
Albrecht Seidl
Fabian Wagner
Andreas Ortner
Frank-Thomas Lentes
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Schott AG
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Schott AG
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Priority to DE102015116848.0A priority Critical patent/DE102015116848A1/en
Publication of DE102015116848A1 publication Critical patent/DE102015116848A1/en
Pending legal-status Critical Current

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/60Preliminary treatment
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50Working by transmitting the laser beam through or within the workpiece
    • B23K26/53Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B23MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23KSOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00Working by laser beam, e.g. welding, cutting or boring
    • B23K26/50Working by transmitting the laser beam through or within the workpiece
    • B23K26/55Working by transmitting the laser beam through or within the workpiece for creating voids inside the workpiece, e.g. for forming flow passages or flow patterns
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B33/00Severing cooled glass
    • C03B33/02Cutting or splitting sheet glass or ribbons; Apparatus or machines therefor
    • C03B33/0222Scoring using a focussed radiation beam, e.g. laser
    • CCHEMISTRY; METALLURGY
    • C03GLASS; MINERAL OR SLAG WOOL
    • C03BMANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B33/00Severing cooled glass
    • C03B33/06Cutting or splitting glass tubes, rods, or hollow products

Abstract

The invention relates to a method for producing a workpiece from a dielectric material, which has at least one zone with defined set strength, wherein the zone of defined strength has cavities, as well as a workpiece produced according to the invention and its use.

Description

  • Field of the invention
  • The invention relates to a method for producing a workpiece from a dielectric material, which has at least one zone of defined strength formed, a dielectric workpiece with at least one zone defined defined strength and its use.
  • Background of the invention
  • Breaking or separating dielectric materials, such as silicon wafers or glass sheets, requires the presence of a weak point in the material. Unless an uncontrolled cracking or shattering is to take place, the crack that opens must either be tightly guided or a damage along the line to be separated into the workpiece or on its surface must be introduced. To introduce such a vulnerability into a material, there are a number of methods. In the simplest case and often described, this may be a scribe placed mechanically on the surface of the workpiece, e.g. with a scratched diamond or a grinding wheel. Based on this method, it is also possible to apply correspondingly effective depressions by means of superficially acting laser radiation, for example by ablation of the glass body by means of a focused laser of suitable wavelength and power, or by local targeted heating and cooling, in order to further increase or permanently introduce microcracks to open.
  • For example, this describes EP 0890554 B1 a method in which by means of pulsed laser radiation of suitable wavelength and suitable pulse length and laser power with suitable beam shaping cracks can be selectively generated in the interior of a glass body to serve as a starting defect for subsequent separation or breaking. Further, it describes that the strength of these introduced defects can be adjusted by appropriately selecting the defect-determining parameters such as laser power and beam shaping. Thus, it is possible to introduce defined cracks, for example along fault lines in a glass of any geometry such as flat glass or in tube glass or other moldings such as ampoules, without these defects have a connection to the environment. This excludes or at least greatly reduces subsequent uncontrolled crack growth, for example due to the action of moisture. The cracked defect in the interior is preferably applied oblong in the later desired direction of propagation of the defect and can be caused by the action of a single pulse or by a plurality of successive pulses. The arrangement of many such cracks side by side along the desired tear line dictates the later fracture surface.
  • Recent patents also describe various other execution of the basic features already in the EP 0890554 B1 described technical teaching.
  • For example, this describes US 6,787,732 B1 a method and apparatus for cutting brittle materials. In this case, a UV laser is used, which is moved during the cutting process along a predetermined line in the workpiece such that a cutting of the workpiece takes place, wherein the focal position of the laser beam is changed in the material, so that a crack is created, which is scarce extending below the first surface of the workpiece to almost the second surface of the workpiece. The change of the focus position is effected by a relative movement of the laser beam to the workpiece. With the in the US 6,787,732 B1 In this case, cracks are applied in the material, wherein each of these cracks is not caused by a single laser pulse, but by a plurality of such pulses, but at least one per changed focal position of the laser beam in the material.
  • Furthermore, the describes US 8,530,786 B2 a method for processing transparent material with an ultrashort pulse laser, wherein defects are applied here in a workpiece, along which a subsequent separation can take place. The control of the defect formation is made possible by the beam shaping of the laser beam.
  • The international patent application WO 2012/006736 A2 describes a method for processing a transparent substrate to prepare a separation step. Here, by means of a laser filaments are generated in the interior of the substrate, wherein the formation of trench-like depressions on at least one surface of the substrate is possible. The filaments form depending on the setting of the laser parameters due to a self-focusing of the laser beam in the interior of the substrate, whereby the formation of multiple filaments behind each other in the substrate is possible. Along the defect line thus generated, the substrate is separated in a further step.
  • Furthermore, the describes US 2005/0173387 A1 a method and apparatus for laser processing a workpiece, wherein the workpiece is cut along a predetermined line. In the interior of the workpiece to be cut is thereby by the Laser treatment generates a defect zone, this defect zone may be formed, for example, as a crack or melting zone or as a zone with refractive index or structural change.
  • All of the abovementioned patents aim at their application to the safe, complete separation of the glass body with good quality of the fracture surfaces. However, further applications require a more targeted, defined pre-damage of the workpiece, for example, to ensure a certain function after a previous damage, for example, to break only when a defined load occurs. However, this is not possible with the known defects. Although the defects that form in the defect zones, for example microcracks, reproducibly lead to damage to the workpiece, so that cutting thereof is facilitated, it is not possible to set reproducibly in this manner in which subsequent mechanical stress the break actually occurs.
  • This leads in particular to those workpieces which are not yet separated immediately after the laser processing, but are to be subjected to further processing and processing steps, to difficulties. Examples of such workpieces are, for example, rupture disks, which are used in particular in storage boxes of emergency keys or for securing fire alarm buttons, of importance, but also for substrates which are coated, for example, in subsequent steps before a separation takes place.
  • Thus, there is a need for a method which makes it possible not only to generate defects or defect line, which serve for the subsequent separation of a glass body, but with the defects and defect lines are selectively and reproducibly generated so that with the creation of a defect or a line of defects is also specified or fixed the breaking force required for later separation.
  • Object of the invention
  • It is an object of the invention to provide a method with which zones of defined breaking strength can be introduced into a dielectric workpiece and to provide a dielectric workpiece according to the invention. Another aspect of the invention relates to the use of a dielectric workpiece according to the invention with at least one zone of defined strength.
  • Summary of the invention
  • The invention is achieved by a method according to claim 1, a workpiece according to claim 14 and its use according to claims 24 to 26. Preferred embodiments can be found in the respective subclaims.
  • The method according to the invention for producing a dielectric workpiece which has at least one zone of defined strength, wherein the strength of the workpiece in the region of the zone with defined strength is reduced in the regions outside the zone of defined strength, comprises at least the following steps :
    • a) providing a workpiece of a dielectric material having a first and a second surface,
    • b) determining the course of the at least one zone with a defined set strength,
    • c) provision of a laser processing apparatus, wherein the laser is designed as a short-pulse or ultra-short pulse laser and emits a laser radiation having a wavelength in the transparency region of the workpiece and further comprises a beam shaping device for beam shaping, in particular for focusing the laser radiation, has
    • d) action of the laser radiation on the workpiece in the form of a laser pulse as a single pulse or in the form of bursts, that is to say laser pulses resolved in partial pulses whose energy content can be adjusted flexibly, such that the laser pulse generates a cavity in the workpiece,
    • e) movement of the laser radiation relative to the workpiece in accordance with the course defined in step b), and
    • f) repetition of steps d) and e), so that in the zone cavities and between the cavities arranged webs are obtained.
  • The cavities are thereby obtained as being substantially tubular, i. their length is greater than their diameter. Furthermore, the regions of the dielectric material which enclose the cavities at least partially have a greater density than the regions which are outside the zone of defined set strength. The cavities also each have the same spatial extent and the same position relative to the surfaces of the workpiece.
  • The formation of cavities causes the weakening of the material due to microcracks in the damage zone recedes. Rather, the greatest damage to the workpiece and thus the decisive lowering of the Strength controlled by the size and location of the cavities reproducible.
  • In one embodiment of the invention, a nonlinear-optical interaction of laser radiation with the workpiece takes place in such a way that a complete plasma formation and / or plasma explosion takes place in the workpiece, so that a cavity exists in the workpiece after plasma formation has taken place.
  • In a further embodiment of the invention, the focusing device of the laser processing device is adjusted such that during the laser pulse, the laser radiation is focused in the form of a line focus, wherein the line focus is characterized by a channel of high light intensity, which has a length of 10 mm or less and a diameter of 10 microns or less.
  • The position of the cavities in the workpiece, in particular the position of the cavities relative to the surfaces of the workpiece is adjustable in a further embodiment of the invention by varying the distance of beam shaping devices relative to the workpiece or generally by changing the focus position of the focusing optics. For example, in a multi-lens system, the change in focus position without changing the distance between the front lens and the workpiece can be changed.
  • According to a further embodiment of the invention, the method is thus characterized in that the position of the cavities relative to the surfaces of the workpiece is adjustable by varying the position of the focus of the optical system used, in particular by changing the distance of the beam shaping device relative to the workpiece and / or by varying the distances of the lenses within a multi-lens system.
  • According to a further embodiment of the invention, the beam shaping device comprises a converging lens and / or an axicon and / or a diffractive optical element (DOE) and / or a computer-generated hologram (cgH).
  • According to one embodiment of the invention, the resulting strength of the zone of the workpiece, which has a defined set strength, adjustable by the width of the webs between the individual cavities.
  • The ratio of the average width of the webs to the mean lateral dimension of the cavities is preferably 20 or less, preferably 10 or less, and particularly preferably 5 or less.
  • Furthermore, the average lateral dimension of the cavities is preferably 0.1 to 5 times the laser wavelength used, preferably 0.2 to 2 times and particularly preferably 0.5 to 1 times the laser wavelength used.
  • In a further embodiment of the invention, the method is carried out in such a way that both the first and the second surface of the workpiece are continuously formed as a closed, preferably polished, in particular mechanically or fire-polished, surface in the zone with defined set strength.
  • Furthermore, in a further embodiment of the invention, however, it is also possible to carry out the method in such a way that the cavities are designed as tubes open at least on one side. In this case, therefore, at least one upper side of the workpiece has holes. However, it is also possible to carry out the method in such a way that the cavities are formed as continuous channels, that is, they pierce the entire thickness of the workpiece.
  • According to a further preferred embodiment of the invention, the generation of the cavities in the at least one zone of defined strength is carried out with a laser pulse which is divided into more than three bursts, preferably more than four bursts and more preferably more than six bursts. Surprisingly, experimental investigations have shown that with increasing burst number the fluctuation range of the breaking stresses decreases and vice versa the Weibull modulus increases correspondingly to the associated distribution. Weibull modulus values greater than 5, greater than 8, or even greater than 10 are achieved. The distribution of the fracture stresses of workpieces obtained by the method according to the invention thus has a Weibull modulus of greater than 5, preferably greater than 8 and more preferably greater than 10.
  • According to yet another preferred embodiment of the invention, the generation of the cavities in the at least one zone of defined strength with a frequency of the bursts of more than 5 MHz, preferably more than 20 MHz, more preferably more than 50 MHz. Also in this way, i. by a reduced time interval of the action of the laser radiation on the workpiece, the fluctuation range of the breaking stresses inventively produced workpieces can be further reduced.
  • The workpiece obtained by the method according to the invention is formed from a dielectric material and has at least one zone in which the strength has been set in a defined manner. The strength in this zone is designed such that it is lower than in the areas adjacent to the zone. The zone has cavities, wherein the cavities are formed substantially tubular like that their length is greater than their diameter. The cavities are arranged along a line, wherein there are webs between the cavities, which delimit the individual cavities from each other. The regions of the dielectric material which enclose the cavities have at least partially a greater density than the regions which are located outside the zone with a defined set strength.
  • In one embodiment of the invention, the cavities have a diameter between 0.2 and 2 .mu.m, preferably between 0.5 and 1 .mu.m, wherein the geometric configuration of the cavities by varying the number of bursts and / or by varying the energy distribution between the individual Bursts is adjustable.
  • In a further embodiment of the invention, the ratio of the average width of the webs to the mean lateral dimension of the cavities has values of 20 or less, preferably 10 or less and particularly preferably 5 or less.
  • The cavities may be formed both from continuous tubes, i. such that the cavities completely pierce the workpiece. But it is also possible that the cavities are formed only as a tube which is open only to one side; or the cavities lie as closed cavities completely in the interior of the workpiece, so that the surface of the workpiece is continuously formed as a closed, preferably even as a polished, for example as a mechanical or fire-polished surface.
  • In this case, in one embodiment of the invention, the workpiece can be substantially disk-shaped.
  • In a further embodiment of the invention, the workpiece is present as a three-dimensionally shaped shaped body, wherein the three-dimensionally shaped hollow body is preferably present as a closed hollow body.
  • Preferably, the workpiece is made of glass, for example of an alumino or borosilicate glass or a thermally or chemically toughened alumino or borosilicate glass.
  • In a preferred embodiment of the invention, the workpiece has a plurality of zones defined defined strength, wherein the zones of defined strength are arranged like a net, for example in the form of a honeycomb pattern.
  • If such a net-like arrangement of a plurality of zones of defined strength is present on a workpiece, wherein the individual zones each have different strengths or can also be designed such that they have substantially the same strength within the usual manufacturing tolerances, the surfaces of the workpiece are preferred as continuously closed, preferably polished, in particular mechanically or fire-polished, surfaces formed, ie the cavities are present as closed cavities in the interior of the workpiece.
  • Workpieces according to the invention can find a variety of applications. For example, it is possible to use such a workpiece as a viewing window, for example as a shaping disk in a vehicle or as a rupture disk for storage boxes, for example for emergency keys. Securing emergency buttons is also possible.
  • The workpiece can be designed so that, if the force required for the fracture has been exceeded, the workpiece is controlled into many small parts, in which case the parts are so small that the risk of injury is reduced. This is particularly advantageous when the workpiece is to be used as a windscreen in a vehicle.
  • In a further embodiment of the invention, it is also possible to laterally illuminate a viewing window, which was provided with at least one zone of defined strength by the method according to the invention, in such a way that the at least one zone of defined strength is made visible. The cavities present in the zones of defined strength act as scattering centers for the laterally irradiated light, so that in this way, for example, the point of attack for removing an emergency key can be made particularly recognizable.
  • Furthermore, workpieces according to the invention can find use, for example, as substrate materials in the chip industry. The use of such defined previously damaged substrates offers the advantage that the substrate can initially be processed without restrictions, after processing, for example, different coating processes, the individual components can then be easily separated along the previously applied damage lines. If wet-chemical processes are also used for coating, it is advisable that the cavities are in the form of closed cavities or are designed only as tubes open to one side. In this way it can be prevented that there is premature failure of the substrate due to stress corrosion cracking.
  • Another use is ampoules, in particular ampoules, find use as Pharmapackmittel. The zone of defined strength is preferably applied in such a way that the cavities have as little as possible any contact with moisture in order to avoid failure of the ampoule by stress corrosion cracking. Consequently, the cavities are preferably formed as open only on one side tubes or as a completely closed cavity.
  • example
  • In the following, the invention will be described in more detail by means of an exemplary representation.
  • The workpiece is a flat glass made of alumino-silicate glass with a thickness of 0.55 mm. This should be provided with a zone of defined strength such that the strength in the zone is below that having the regions of the glass which are outside the zone of defined strength. The zone of defined strength in this case has cavities, which each have the same spatial extent and the same position with respect to their position relative to the surface of the flat glass.
  • To create the cavities, a pulsed laser with the following parameters is used: wavelength 1064 nm pulse duration 10 ps pulse energy 100 μJ repetition 100 kHz beam quality 1.2
  • Here, the single pulse is driven in the so-called burst mode, i. divided into two sub-packages, the first sub-pulse contains two-thirds of the total energy. The second partial pulse follows 20 ns after the first partial pulse.
  • For beam shaping, a spherical symmetrical biconvex lens with a paraxial focal length of 20 mm and a diameter of 25 mm is used. The expanded laser beam diameter in front of the lens is 12 mm. Due to the spherical aberration in front of the paraxial focus, a focus area behind the lens forms a high-intensity channel several millimeters long with a small diameter of just a few μm.
  • Before irradiation of the workpiece with the laser, the course of the predetermined breaking point, i. of the zone defined by defined, i. lesser strength compared to the non-machined workpiece to be configured determined.
  • The glass is moved at a speed of 0.5 m / s relative to the laser beam. In this way, cavities are formed in the glass, which have an inner diameter of 1.5 to 2 microns and between them webs arise, which are 5 microns wide.
  • Depending on the selected distance between the workpiece and the laser cavities can be obtained, which as a continuous tube, i. with openings on both sides of the workpiece, are configured, or present as a completely closed cavity or also have an opening to one side of the workpiece.
  • In the present example, the lens-facing surface of the workpiece is positioned 1.1 mm in front of its paraxial focus, with the cavities completely penetrating the workpiece. Shorter channels can be obtained by reducing the distance between the workpiece and the lens.
  • Furthermore, it is possible to determine at least approximately in advance which strength is obtained with which configuration of the zone of defined strength.
  • The combination of the precisely adjustable defect position in the zone of defined strength with the resulting strength is carried out by way of example and simplified by the following relation
    Figure DE102015116848A1_0002
  • In this case, σ B denotes the breaking stress in the case of a tensile surface of the workpiece; a is the injury depth. The relationship described under (1) applies only in a first approximation. Further in-depth models are known and widely described in the literature.
  • Description of the drawings
  • It shows
  • 1 a schematic representation of the setting of the defect depth,
  • 2 a schematic representation of a workpiece with differently shaped cavities according to the invention,
  • 3 the beam shaping of a laser in carrying out the method according to the invention,
  • 4 the approximate decrease of the breaking strength with increasing defect depth,
  • 5 a representation of a workpiece produced by the method according to the invention with a zone of defined strength,
  • 6 an electron micrograph of the fracture edge of a workpiece according to the invention,
  • 7 a schematic representation of a visor according to the invention,
  • 8th a schematic representation of an ampoule according to the invention,
  • 9 a schematic representation of a windshield for a vehicle according to the invention,
  • 10 a representation of the relative standard deviation of the strength of a workpiece according to the invention as a function of the number of bursts, and
  • 11 a representation of the standard deviation of the strength in MPa of a workpiece according to the invention as a function of the number of bursts.
  • 1 shows the schematic, not to scale representation of the setting of the depth of defect in the inventive method. The laser beam 1 is doing by a beam shaping optics or focusing 2 , pictured here as a biconvex condenser lens 2 formed such that behind the paraxial focus of the beam shaping optics 2 a narrow zone of high intensity 4 or even line focus 4 is obtained. By the distance between the beam shaping optics 2 and the workpiece 3 or, in general, the position of the focus of the optics used, for example, with respect to the front lens is varied by varying the distances within a multi-lens system, the position of the line focus 4 relative to the surfaces 31 . 32 of the dielectric workpiece 3 be set. For better clarity, the surfaces were 31 . 32 only in the right area of the 1 designated. The location of the line focus 4 in the workpiece 3 determines the position of the resulting cavities in the process according to the invention 5 (not shown). In the left area of 1 is the narrow zone with high intensity 4 of the laser beam 1 doing so so that in the workpiece 3 only a short cavity is obtained, which as to one side, namely the surface 32 of the workpiece 3 , is open. In the middle range of 1 lies the line focus 4 of the laser beam 1 such that a cavity is obtained, which also as to the surface 32 of the workpiece 3 open tube is designed, this cavity is approximately half the thickness of the workpiece 3 runs. In the right area of the 1 the entire sample is in line focus 4 of the laser beam 1 in that the resulting cavity extends through the entire sample and is designed as a tube which leads both to the surface 31 as well as the surface 32 of the workpiece 3 is open.
  • 2 shows schematically, not to scale, different cavities 5 in a dielectric workpiece 3 , In the left area of 2 is a cavity 5 shown in which the laser beam 1 (not shown) has been shaped so that the line focus 4 (not shown) completely in the workpiece 3 However, although the thickness of the workpiece 3 was greater than the length of the line focus. In this way became a cavity 5 which is completely inside the workpiece 3 runs, so that at this point the surfaces 31 and 32 of the workpiece 3 are designed as continuous surfaces. Unless the surfaces 31 and 32 of the workpiece 3 In this case, prior to carrying out the method according to the invention as polished surfaces templates, for example by a mechanical or a Feuerpolitur, they are also after carrying out the method according to the invention as such, ie in this case, the quality of the surfaces 31 . 32 not impaired. Also shown is the area 6 around the cavity 5 this being characterized in that the matrix of the workpiece 3 Here at least partially present with a higher density at least partially compared to the untreated matrix. Furthermore, it is also possible in this area for a change in the structure of the dielectric workpiece 3 come, for example in the form of structural changes, for example in the form of partial crystallization or the like. In the middle range of 2 is a cavity 5 represented around which also in comparison to the untreated matrix of the workpiece 3 modified area 6 is trained. The area 6 also has at least partially an at least partially increased density compared to the untreated matrix of the workpiece 3 and can also continue to have other modifications, for example in the form of structural changes. The cavity 5 is designed here as a tube, which to the surface 32 of the workpiece 3 is open. In the right area of the 2 is still a tubular cavity 5 represented around which a modified area 6 is formed, wherein the cavity 5 doing both to the surface 31 as well as the surface 32 of the workpiece 3 is designed to be open. All three in 2 imaged cavities 5 is common that the aspect ratio of their length, in 2 Thus, their lateral dimension in the vertical direction, to its diameter, that is, the lateral dimension in the horizontal direction, is greater than 1, so that long, tubes are obtained with a fairly small average diameter. The mean diameter of the cavities 5 This results in the mean value of its diameter over its entire length.
  • 3 shows a representation of a possible type of beam shaping in the method according to the invention. In the upper left area of the 3 is the laser beam 1 when passing through the beam shaping optics 2 shown here by way of example in the form of a spherical biconvex lens. The spherical aberration of the beam is behind the paraxial focus of the lens 2 a narrow zone of high intensity 4 or a line focus 4 , In the upper right area of the 3 is magnified a representation of the beam path in the narrow zone of high intensity 4 to see, in which case the narrow zone of high intensity 4 within a workpiece 3 runs. At the bottom of the 3 is schematically the spatially resolved course of the intensity of the laser beam 1 in the area of the narrow zone of high intensity 4 shown. The relative intensity of the beam is plotted on the y-axis, and the x-axis indicates the position in the laser beam 1 itself, where the zero point of the x-axis is at the nominal center of the laser beam 1 was laid.
  • 4 shows the decrease in strength in the zone of defined strength obtained with the method according to the invention. The decrease in the breaking strength in the zone of defined strength obtained according to the invention can be approximated by the relation
    Figure DE102015116848A1_0003
    Here, σ B describes the breaking strength and a the depth of defect in the workpiece relative to a reference surface. The greater the depth of the defect, the lower the resulting breaking strength. In the diagram, the breaking strength σ B is plotted on the y-axis, the defect depth a on the x-axis.
  • 5 shows a microscopic representation of a surface of a workpiece obtained according to the invention 3 defined with a zone fixed strength 7 , Here is the strength of the workpiece 3 defined in the zone defined strength 7 less than in the outside of the zone 7 lying untreated areas 71 of the workpiece 3 , The zone of defined strength has cavities 5 on which along a predetermined course along a line in the workpiece 3 were introduced. For clarity, it was waived, all cavities 5 in the zone of defined strength 7 to call. The individual cavities 5 are here by webs 51 separated from each other, wherein the webs 51 are larger than the average diameter of the cavities 5 , The diameter of the cavities 5 is for the example shown here between 1.6 and 2.4 microns.
  • In general, without being limited to the example depicted here, the average diameter of the cavities produced according to the invention lies 5 usually in the single-digit micrometer range and is thus much smaller than their length, which ranges from a few tens of micrometers to the range of several millimeters. Furthermore, the webs 51 between the cavities 5 greater than its diameter, the ratio of the average width of the webs 51 to the mean diameter of the cavities 5 20 or less, preferably 10 or less, and more preferably 5 or less.
  • 6 shows an electron micrograph of a fracture edge 8th a workpiece 3 along a zone defines set strength 7 , The breaking edge 8th is characterized by a roughness in the micrometer range, preferably in the single-digit micrometer range, indicated as a square average roughness, which is determined with an atomic force microscope, profilometer or a white light interferometer or equivalent measurement technique for determining roughness values. When considering the breaking edge of a workpiece according to the invention 3 In particular, its matte, non-shiny appearance, which is due to the roughness in the micrometer range, stands out with the unaided eye. Also clearly visible are the tubular cavities 5 or their traces obtained on the breaklines, which pass through the workpiece perpendicular to its surface.
  • In 7 is schematically a rupture disk obtained by the method according to the invention 9 shown. This consists of a dielectric workpiece, in this case a transparent to the visible light formed workpiece, which may for example consist of glass, in which a zone of defined strength 7 formed by cavities 5 , which are arranged along a closed line was introduced. Such a rupture disk can be used for example in systems for emergency key or alarm buttons. Furthermore, it is possible to make visible for better visibility of the point of attack by a lateral illumination, in which case the cavities 5 act as scattering centers.
  • 8th shows the schematic representation of an obtained ampoule according to the invention 10 , in particular a glass ampoule for receiving pharmaceuticals, which has a zone of defined strength. Preference is given to the cavities forming the zone of defined strength, so formed that they are present as closed cavities in the workpiece, so have no opening to one of the surfaces of the workpiece. In this way premature failure of the ampule due to breakage due to stress corrosion cracking can be avoided.
  • 9 shows the schematic representation of a viewing window according to the invention 11 For example, for a vehicle, here the zones of defined strength 7 in the form of a network 12 available. The network 12 is here in the form of honeycombs, however, depending on the configuration, other arrangements, for example as a right-angled crossing a plurality of straight lines, possible. The lens 11 In the present illustration, FIG. 1 shows one of a black coating 111 formed frame, as is customary for example in windscreens for vehicles, wherein the coating with a frame color preferably takes place before the generation of the zones of defined strength, but also lenses without such a border are conceivable. Furthermore, the lens can also be present as a not completely flat disc, but have a slight curvature, as is also possible for example in the case of viewing windows for vehicles. The cavities in the zones of defined strength can in each case be formed as continuous cavities, as tubes open on one side or as closed cavities formed in the workpiece, wherein in an embodiment of the workpiece as a viewing window for, for example, a vehicle, at least one surface of the workpiece preferably has no openings should have.
  • Furthermore, it has been shown in experimental investigations that with increasing number of bursts, the fluctuation range of the breaking stresses for inventively obtained workpieces decreases and vice versa the Weibull modulus of the associated distribution increases accordingly. Weibull modulus values greater than 5, greater than 8, or even greater than 10 are achieved.
  • In 10 this is shown by way of example for the representation of the relative standard deviation of the fracture stresses according to the invention obtained workpieces as a function of the number of bursts. While the relative standard deviation at a burst number of two is about 0.375, a doubling of the burst number already results in a decrease in the relative standard deviation to a value of about 0.1. Further doubling results in a further decrease of the relative standard deviation to about 0.075.
  • In 11 this is further shown for the standard deviation in MPa of the breaking stress according to the invention obtained workpieces as a function of the choice of bursts. While with only two bursts this has a value of 160 MPa, it drops to a value of less than 20 MPa with 4 bursts and becomes even lower with a further doubling of the burst number to now eight bursts.
  • LIST OF REFERENCE NUMBERS
  • 1
    laser beam
    2
    Beam shaping optics
    3
    Dielectric workpiece
    31, 32
    Surfaces of the workpiece
    4
    Narrow zone of high intensity, line focus
    5
    cavity
    51
    Bridge between two cavities
    6
    the cavity enclosing area of the workpiece
    7
    Zone of defined strength
    71
    untreated areas of the workpiece outside the zone (s) of defined strength
    8th
    breakline
    9
    rupture disc
    10
    ampoule
    11
    Window
    111
    Rahme
    12
    Net, formed of zones of defined strength
  • QUOTES INCLUDE IN THE DESCRIPTION
  • This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.
  • Cited patent literature
    • EP 0890554 B1 [0003, 0004]
    • US 6787732 B1 [0005, 0005]
    • US 8530786 B2 [0006]
    • WO 2012/006736 A2 [0007]
    • US 2005/0173387 A1 [0008]

Claims (26)

  1. Method for producing a workpiece ( 3 ) of a dielectric material comprising at least one zone ( 7 ) of defined strength, comprising at least the following steps: a) providing a workpiece ( 3 ) of a dielectric material having a first surface ( 31 ) and a second surface ( 32 b) determining the course of the at least one zone ( 7 c) provision of a laser processing device, wherein the laser is designed as a short-pulse or ultra-short pulse laser and a laser radiation ( 1 ) having a wavelength in the transparency region of the workpiece ( 3 ) and further via a beam shaping device ( 2 ) for beam shaping, in particular for focusing the laser radiation, d) action of laser radiation on the workpiece ( 3 ) in the form of a laser pulse as a single pulse or in the form of bursts, that is to say of laser pulses resolved in partial pulses whose energy content can be adjusted flexibly such that the laser pulse forms a cavity ( 5 ) in the workpiece ( 3 ), e) movement of the laser radiation ( 1 ) relative to the workpiece ( 3 ) according to the course defined in step b), and f) repeating steps d) and e) so that in the zone ( 7 ) Cavities ( 5 ) and between the cavities ( 5 ) arranged webs ( 51 ), the cavities ( 5 ) are substantially tubular, so that their length is greater than their diameter, and the regions ( 6 ) of the dielectric material containing the cavities ( 5 ), at least partially have a greater density than the regions ( 71 ), which are outside the zone ( 7 ) with defined set strength, and furthermore the cavities ( 5 ) each have the same spatial extent and the same position relative to the surfaces ( 31 . 32 ) of the workpiece ( 3 ) exhibit.
  2. Method according to claim 1, wherein a non-linear-optical interaction of the laser radiation ( 1 ) is carried out with the workpiece such that a complete plasma formation and / or plasma explosion takes place in the workpiece, so that after the formation of plasma and / or plasma explosion in the workpiece ( 3 ) a cavity ( 5 ) is present.
  3. Method according to one of claims 1 or 2, wherein the focusing device ( 2 ) is set such that during the laser pulse, the laser radiation ( 1 ) in the form of a line focus ( 2 ), the line focus ( 2 ) is characterized by a high light intensity channel having a length of 10 mm or less and a diameter of 10 μm or less.
  4. Method according to one of claims 1 to 3, characterized in that the position of the cavities ( 5 ) relative to the surfaces of the workpiece ( 3 ) is adjustable by the variation of the position of the focus of the optical system used, in particular by a change in the distance from the beam shaping device ( 2 ) relative to the workpiece ( 3 ) and / or by varying the distances of the lenses within a multi-lens system.
  5. Method according to one of claims 1 to 4, characterized in that the beam shaping device ( 2 ) comprises a condenser lens and / or an axicon and / or a diffractive optical element and / or a computer-generated hologram.
  6. Method according to one of claims 1 to 5, characterized in that the resulting strength of the zone ( 7 ) with defined strength of the dielectric workpiece ( 3 ) by the width of the webs ( 51 ) between the individual cavities ( 5 ) is adjustable.
  7. Method according to one of claims 1 to 6, characterized in that the ratio of the average width of the webs ( 51 ) to the mean diameter of the cavities ( 5 ) Is 20 or less, preferably 10 or less, and more preferably 5 or less.
  8. Method according to one of claims 1 to 7, characterized in that the average diameter of the cavities ( 5 ) is 0.1 to 5 times the laser wavelength used, preferably 0.2 to 2 times and particularly preferably 0.5 to 1 times the laser wavelength used.
  9. Method according to one of claims 1 to 8, wherein the surfaces ( 31 ) and ( 32 ) in the area of the zone ( 7 ) are formed with defined set strength continuously as a closed, preferably polished, in particular mechanically or fire polished, surface.
  10. Method according to one of claims 1 to 8, wherein the cavities ( 5 ) are formed as open at least on one side tube.
  11.  Method according to one of claims 1 to 10, wherein the generation of the cavities takes place with a laser pulse which is divided into more than three bursts, preferably more than four bursts and more preferably more than six bursts.
  12. Method according to one of Claims 1 to 11, wherein the generation of the cavities takes place with a frequency of the bursts of more than 5 MHz, preferably of more than 20 MHz, particularly preferably of more than 50 MHz.
  13.  Method according to one of claims 1 to 12, wherein the distribution of the fracture stresses on workpieces according to the invention has a Weibull modulus of greater than 5, preferably greater than 8 and more preferably greater than 10.
  14. Workpiece ( 3 ) of a dielectric material comprising at least one zone ( 7 ) with defined strength, the strength in the zone ( 7 ) is designed to be lower than that to the zone ( 7 ) adjacent areas ( 71 ) and where the zone ( 7 ) is formed in such a way that it has cavities ( 5 ), wherein the cavities ( 5 ) are formed substantially tubular so that their length is greater than their mean diameter, wherein the cavities ( 5 ) are arranged along a line and between the cavities ( 5 ) Webs ( 51 ) and where the areas ( 6 ) of the dielectric material containing the cavities ( 5 ), at least partially have a greater density than the regions ( 71 ), which are outside the zone ( 7 ) with defined set strength.
  15. Workpiece ( 3 ) according to claim 14, wherein the cavities ( 5 ) have a diameter between 0.2 and 2 microns, preferably between 0.5 and 1 micron.
  16. Workpiece ( 3 ) according to one of claims 14 or 15, wherein the ratio of the average width of the webs ( 51 ) to the mean diameter of the cavities ( 5 ) Is 20 or less, preferably 10 or less, and more preferably 5 or less.
  17. Workpiece ( 3 ) according to one of claims 14 to 16, wherein at least one of the surfaces ( 31 ) or ( 32 ) in the area of the zone ( 7 ) with defined set strength of the workpiece ( 3 ) is continuously formed as a closed, preferably polished, in particular mechanically or fire-polished, surface.
  18. Workpiece ( 3 ) according to one of claims 14 to 16, wherein the cavities ( 5 ) are formed as continuous cavities.
  19. Workpiece ( 3 ) according to one of claims 14 to 18, wherein the workpiece ( 3 ) is disc-shaped.
  20. Workpiece ( 3 ) according to one of claims 14 to 18, wherein the workpiece ( 3 ) is formed as a three-dimensional molded body, preferably as a closed hollow body.
  21. Workpiece ( 3 ) according to one of claims 14 to 20, wherein the workpiece ( 3 ) consists of glass, preferably an alumino or borosilicate glass or a thermally or chemically prestressed alumino or borosilicate glass.
  22. Workpiece ( 3 ) according to one of claims 14 to 21, wherein the workpiece ( 3 ) several zones ( 7 ) with defined strength, the zones ( 7 ) defined strength are arranged net-like.
  23. Workpiece ( 3 ) according to claim 22, wherein at least one of the surfaces ( 31 ) and ( 32 ) of the workpiece ( 3 ) in the zone ( 7 ) defined strength as consistently closed, preferably polished, in particular mechanically or fire polished, surface is present.
  24. Use of a workpiece ( 3 ) according to one of claims 14 to 19 and 21 to 22 as a viewing window ( 11 ), for example as a windshield in a vehicle, or as a rupture disk ( 9 ) for storage boxes or autoclave devices.
  25. Use of a workpiece ( 3 ) according to one of claims 14 to 19 and 21 to 22 as a substrate material, for example for the production of miniaturized components, in particular miniaturized electronic components, or slides or biochip.
  26. Use of a workpiece ( 3 ) according to one of claims 14 to 17 and 20 to 23 as pharmaceutical packaging, in particular as an ampoule ( 10 ).
DE102015116848.0A 2015-10-05 2015-10-05 Dielectric workpiece with a zone of defined strength and method for its production and its use Pending DE102015116848A1 (en)

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WO2018210519A1 (en) 2017-05-19 2018-11-22 Schott Ag Component comprising glass or glass ceramic, having pre-damaged points along a predetermined dividing line, method and device for producing the component and use thereof
WO2019158488A1 (en) 2018-02-15 2019-08-22 Schott Ag Method and device for inserting a separation line into a transparent, brittle-fracture material, and element that can be produced according to the method and is provided with a separation line
EP3560896A1 (en) * 2018-04-24 2019-10-30 Schott Ag Method and device for the preparation of glass hollow body products and glass hollow body products and their use

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EP0890554B1 (en) 1997-07-07 2002-01-02 Schott-Rohrglas GmbH Method for making a breaking line on a glass body
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WO2018210519A1 (en) 2017-05-19 2018-11-22 Schott Ag Component comprising glass or glass ceramic, having pre-damaged points along a predetermined dividing line, method and device for producing the component and use thereof
DE102018109302A1 (en) 2017-05-19 2018-11-22 Schott Ag Component comprising glass or glass ceramic, arranged along a predetermined separation line Vorschädigungen, method and apparatus for producing the component and its use
WO2019158488A1 (en) 2018-02-15 2019-08-22 Schott Ag Method and device for inserting a separation line into a transparent, brittle-fracture material, and element that can be produced according to the method and is provided with a separation line
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