METHOD FOR SEPARATING SUBSTRATES AND ASSOCIATED SUBSTRATES

Description

[0001] The invention relates to a method for laser-assisted separation of substrates made of glass, glass-ceramic, or silicon, in which damage is introduced into the substrate at intervals along a predetermined separation line using a pulsed laser beam. The invention further relates to a workpiece formed as a glass product, a glass-ceramic product, or a silicon product, which has damages spaced apart along a separation line.

[0002] A widely used cutting process in the glass industry is mechanical scoring and breaking. This process is cost-effective but essentially limited to straight cuts. After breaking, the edges often lack sufficient quality, which may require extensive post-processing, such as grinding or polishing.

[0003] Another process is waterjet cutting, which, while allowing for free-form geometries, is relatively slow and expensive, with limited quality, so further edge processing is typically necessary with this process as well. Waterjet cutting is therefore primarily used for complex geometries that cannot be produced using scoring and breaking, and possibly subsequent post-processing.

[0004] In the thermal laser scribing process, the glass is heated along the cutting line using a CO2 laser, for example, and then immediately cooled down again. This makes it possible to achieve high edge quality while simultaneously producing freeform geometries, provided the curvature radii of the cutting edge are not too small. However, laser scribing is not suitable for thicker glasses, or only with significant quality loss, and especially not for glasses with a low thermal expansion coefficient.

[0005] In this context, the laser filamentation process appears particularly promising. This involves using an ultrashort pulse laser to create a dividing line, e.g., in the form of a perforation, in the glass.

[0006] As described in US2013 / 126573 A1 or WO 2012 / 006736 A2, filaments can be created in a transparent substrate using a pulsed, focused laser beam. A path formed by multiple filaments allows the substrate to be separated. A filament is created using a high-energy, short laser pulse, and it is assumed that the nonlinear optical Kerr effect leads to self-focusing of the laser beam, thereby causing plasma formation.

[0007] US 2015 / 165548 A1 describes methods for beveling and / or chamfering an edge of glass or another substrate using lasers. A first method uses an ultrashort pulse laser and, optionally, a CO2 laser. A second method is based on thermal stresses using various combinations of ultrashort pulse and / or CO2 lasers. A third method is based on stresses induced by ion exchange.

[0008] US 2014 / 340730 A1 describes methods for cutting tempered glass using a laser, as well as tempered glass with edges that show signs of a laser cutting process.

[0009] DE 10 2012 110 971 A1 also describes a method for preparing transparent workpieces for separation, in which filament structures extending transversely through the workpiece and arranged in a row are created by ultrashort laser pulses along a predetermined breaking line.

[0010] Once a filament path, particularly in the form of a pre-damage line or a perforation line, has been introduced into the glass by means of laser filamentation, the glass can be separated in a further cleaving step. The filament path is traced using a CO2 laser, for example, so that the glass separates along the filament path and thus along a predetermined separating line. However, errors can occur during the cleaving step, particularly with complex geometries or materials with a low thermal expansion coefficient. For example, the crack does not follow the pre-introduced separating line and tears out, or the crack does not start or breaks off. It has been shown that such problems can manifest themselves differently with different types of glass, i.e. can sometimes depend on the particular glass to be separated.

[0011] The invention therefore has the general object of optimizing the process of laser filamentation with subsequent cleaving step, in particular with regard to the material to be separated.

[0012] One aspect of the object of the invention is to improve the quality of the separating edge.

[0013] According to the invention, this object is achieved by the subject matter of the independent claims. Advantageous developments of the invention are the subject matter of the dependent claims.

[0014] The invention accordingly relates to a method for separating a substrate made of brittle material, namely glass, glass ceramic and / or silicon, wherein damage is introduced into the substrate along a predetermined separating line with at least one pulsed laser beam at a distance from one another.

[0015] Accordingly, filamentary damage is created adjacently along a dividing line in the volume of the substrate, wherein the substrate can be designed, in particular, as a flat glass element, a flat glass-ceramic element, or a flat silicon wafer. The filamentary damage is created by laser pulses from a laser, in particular by the laser pulses generating a plasma in the volume of the glass. The material of the substrate is transparent to the laser pulses, and the points of impact of the laser pulses on the substrate are moved across its surface along the dividing line.

[0016] When introducing the damage, both the average distance between adjacent damages and the number of laser pulses for generating each of the damages are selected such that (a) the fracture stress σ B for separating the substrate along the separation line is smaller than a first reference stress σ R1 which depends on the respective substrate, (b) the edge strength σ K of the separation edge obtained after separation is greater than a second reference stress σ R2 which depends on the respective substrate and (c) the substrate can be separated after the introduction of the damages by the action of a stress along the separation line.

[0017] In other words, laser filamentation is performed with regard to the breaking stress of the substrate, with the number of pulses fired at individual perforation points and the spacing of the filaments being preselected accordingly. Furthermore, it is also possible to preselect the time difference between the individual pulses for the creation of a filament.

[0018] The fracture stress σ B is the stress required to separate the substrate along the separation line after the damage has been introduced, i.e., to open the filamentation channel. The fracture stress is determined by σ B < σ R1 , where the first reference stress σ R1 denotes a value dependent on the substrate, in particular a value that depends on the substrate material and / or its properties.

[0019] Furthermore, the filamentation parameters can also influence the edge strength. The edge strength σ K is the stress that must be applied to drive a crack into the substrate with the separation edge obtained after separation and to cause the substrate to break. The edge strength is determined by σ K > σ R2 , where the second reference stress σ R2 again denotes a value that depends on the substrate material and / or its properties.

[0020] According to the invention, it is provided that (A) the first and the second reference stress σ R1 = σ R2 are identical and are specified as a maximum thermal stress σ th which depends on the material of the substrate or, in the case of a chemically or thermally prestressed substrate, as an internal tensile stress σ CT defined by the properties of the prestressed substrate, wherein in the first case the maximum thermal stress σ th can be determined according to the formula σ th = 0.5·α·E·(T g -100°C), where a denotes the thermal expansion coefficient of the material of the substrate, E denotes the elastic modulus of the material of the substrate and T g denotes the glass transition temperature of the material of the substrate and wherein in the second case in the case of a chemically prestressed substrate the internal tensile stress σ CT is determined according to the formula σ CT = (σ CS ·d L ) / (d-2d L ) or in the case of a thermally prestressed substrate according to the formula Formula σ CT = σ CS / 2 can be determined,where σ CS is the surface compressive stress of the prestressed substrate, d L is the penetration depth of the prestress, and d is the thickness of the substrate, or that (B) for the first reference stress, σ R1 ≤ C R1 α E (T g -100°C) applies and for the second reference stress, σ R2 ≥ C R2 α E (T g -100°C), where C R1 and C R2 are reference stress coefficients with C R1 = 0.5 / k and C R2 = 0.5 k and k = 1.5, preferably k = 2, particularly preferably k = 2.5, and where α is the thermal expansion coefficient of the substrate material, E is the elastic modulus of the substrate material, and T g is the glass transition temperature of the substrate material.

[0021] In case (A), it is therefore particularly provided that the first and second reference voltages are identical and are specified as a maximum thermal voltage dependent on the material of the substrate, i.e., σ R1 = σ R2 = σ th . The maximum thermal voltage σ th is understood to be the voltage that can be achieved by selective heating of the substrate, in particular by means of a CO 2 laser.

[0022] The maximum thermal stress σ th can be determined according to the formula σ th = 0.5·α·E·(T g -100°C), where α is the thermal expansion coefficient of the substrate material, E is the elastic modulus of the substrate material and T g is the glass transition temperature of the substrate material.

[0023] Within the framework of a DOE test series, which is discussed in more detail below, it was experimentally confirmed that the cleaving step is particularly successful for samples made of different glasses under the conditions mentioned, in particular σ B < 0.5· α ·E·(T g -100°C) and σ K > 0.5· α ·E·(T g -100°C).

[0024] In case (B) it is provided that for the first reference stress σ R1 ≤ C R1 · α · E · (T g -100°C) applies and for the second reference stress σ R2 ≥ C R2 · α · E · (T g -100°C) applies, where C R1 and C R2 are reference stress coefficients with C R1 = 0.5 / k and C R2 = 0.5*k and k = 1.5, preferably k = 2, particularly preferably k = 2.5 and where α again denotes the thermal expansion coefficient of the material of the substrate, E denotes the elastic modulus of the material of the substrate and T g denotes the glass transition temperature of the material of the substrate.

[0025] Accordingly, it is particularly preferred, for example, that the breaking stress σ B < 0.25 α E (T g -100°C) applies and the edge strength σ K > 0.5 α E (T g -100°C) applies. Even more preferably, the breaking stress σ B < 0.25 α E (T g -100°C) applies and the edge strength σ K > α E (T g -100°C) applies. It is worth mentioning that the breaking stress is further preferably σ B > 1 / 20 α E (T g -100°C).

[0026] For example, if the value of the thermally induced stress of the cleaving step is above the upper limit for the fracture stress, the substrate may relax locally due to its proximity to T g , ie the necessary stress cannot be built up and the cleaving step fails, assuming the mean value of the stress distribution.

[0027] The above statements apply particularly to non-tempered glass substrates. For tempered substrates or glass, however, the value of the thermal expansion coefficient α is less important. The internal tensile stress σ CT ("center tension") is more important.

[0028] In the case of a particularly chemically prestressed substrate, preferably made of glass, it is accordingly provided that the first and the second reference stress are identical and are predetermined as an internal tensile stress defined by the properties of the prestressed substrate, ie σ R1 = σ R2 = σ CT .

[0029] The internal tensile stress σ CT can be determined for a chemically prestressed substrate according to the formula σ CT = (σ CS ·d L ) / (d-2d L ), where σ CS denotes the surface compressive stress (compaction stress) of the prestressed substrate, d denotes the thickness of the substrate, in particular of the flat glass substrate, and d L denotes the penetration depth of the prestress ("depth of layer", DoL), in other words the distance of the zero crossing of the stress from the substrate surface or the thickness of the prestressed layer of the substrate.

[0030] The internal tensile stress σ CT can be determined in a thermally prestressed substrate according to the formula σ CT = σ CS / 2, where σ CS is the surface compressive stress (compaction stress) of the prestressed substrate.

[0031] For the cleaving process, it may therefore be preferable to set the breaking stress lower than the internal tensile stress σ CT , while significantly increasing the edge strength. For the cleaving process, it may therefore be particularly preferable to set the breaking stress lower than the sum of the internal tensile stress σ CT and the thermal stress σ th , while increasing the edge strength, especially significantly.

[0032] Regardless of whether the substrate is pre-stressed or not, after the damage has been applied, a laser beam, preferably a CO2 laser, can be moved along the cleavage line to induce the stress required for separation along the cleavage line. This step is also referred to as the cleaving step and is advantageously carried out using the measures described above.

[0033] By means of the cleaving step, local thermomechanical stresses are induced in the substrate, ie in particular in the glass element, the glass-ceramic element or the silicon element, at or along the dividing line in order to cause crack formation between adjacent filamentary damages, ie to connect adjacent filamentary damages by cracks.

[0034] This allows the perforation to be completed into an at least partial separation line, i.e., an at least partial separation or splitting of the substrate along the separation line can be achieved. Preferably, a complete separation line is achieved.

[0035] With the breaking stress or edge strength set as described above, the conditions for the success of the cleaving step are optimized in a number of aspects.

[0036] Firstly, the perforation line can be successfully separated even in materials with a relatively low thermal expansion coefficient α. Materials or glasses with α < 5·10 -6< K -1< , preferably with α < 4.5·10 -6< K -1< , and particularly preferably with α < 4·10 -6< K -1< , can be successfully separated. This was verified in the DOE experiments described in more detail below.

[0037] Secondly, the lateral deviation of the laser spot from the perforation line can be greater during the cleaving step, i.e., the positional tolerance of the CO2 laser's impact point needs to be less precise without the cleaving step failing. While this lateral deviation should conventionally be less than 500 µm, lateral deviations of up to 3 mm can advantageously be tolerated with the method according to the invention. This was also confirmed in the tests presented below, particularly for materials with α > 4.5·10 -6< K -1< , which were filamented, i.e., perforated, as described.

[0038] Furthermore, the power of the laser used for cleaving can also be advantageously reduced while maintaining the same speed.

[0039] The damage is created using a laser that preferably emits ultrashort laser pulses (USP lasers). The laser pulses create filament-shaped damage precisely along the specified dividing line across the preferably flat substrate by locally destroying the material in the interaction zone with the laser light. The damage is typically formed as defined linear damage, the length of which can be influenced by selecting suitable pulse energies and pulse durations. By generating a plurality of filaments spaced at appropriate intervals, perforation of the material is achieved.

[0040] Such microperforation achieves very high edge quality at the cut edges of the substrate. The process thus represents a precision cutting method that guarantees high and defined edge quality and thus, in particular, leads to high and defined edge strength and flexural strength of the substrate after cutting. The achieved edge qualities are particularly high enough that subsequent grinding of the edges is often unnecessary.

[0041] The damage is generated particularly when the ultrashort pulse laser is operated in burst mode. In this operating mode, the laser pulse is not delivered as a single pulse, but rather as a series of pulses delivered in quick succession, which together form a pulse packet, a so-called burst. Damage is preferably generated by means of a burst.

[0042] Such a pulse packet generally has a slightly higher energy than a single pulse in conventional single-shot operation. However, the pulses of a burst themselves contain significantly less energy than a single pulse. With regard to the pulses within a burst, it can be provided that the pulse energies are flexibly adjustable, in particular that the pulse energies either remain essentially constant, increase, or decrease.

[0043] A suitable laser source according to the present invention is a neodymium-doped yttrium aluminum garnet laser with a wavelength of 1064 nanometers.

[0044] For example, the laser source generates a raw beam with a (1 / e 2<) diameter of 12 mm. A biconvex lens with a focal length of 16 mm can be used as the optics. A suitable beam-shaping optic, such as a Galilean telescope, can be used to generate the raw beam.

[0045] The laser source operates in particular with a repetition rate which is between 1 kHz and 1000 kHz, preferably between 10 kHz and 400 kHz, particularly preferably between 30 kHz and 200 kHz.

[0046] The repetition rate and / or the scanning speed can be selected so that the desired distance between adjacent filamentous lesions is achieved.

[0047] The suitable pulse duration of a laser pulse is in the range of less than 100 picoseconds, preferably less than 20 picoseconds.

[0048] The typical power of the laser source is particularly advantageously in the range of 20 to 300 watts. To achieve the filament-like damage, according to an advantageous development of the invention, a pulse energy of more than 400 microjoules in the burst is used, and furthermore, a total burst energy of more than 500 microjoules is advantageously used.

[0049] When operating an ultrashort pulse laser in burst mode, the repetition rate is the rate at which bursts are emitted. The pulse duration is essentially independent of whether a laser is operated in single-pulse mode or burst mode. The pulses within a burst typically have a similar pulse length to a pulse in single-pulse mode. The burst frequency can be in the interval [15 MHz, 90 MHz], preferably in the interval [20 MHz, 85 MHz], and is, for example, 50 MHz. The number of pulses in the burst can be between 1 and 10 pulses, e.g., 6 pulses.

[0050] Within the scope of the invention, when introducing the damage, the average distance between adjacent damages and the number of laser pulses for generating each of the damages are selected with regard to the fracture stress σ B and the edge strength σ K.

[0051] The number of laser pulses for generating each damage is selected in particular from the interval [1, 20], preferably from the interval [1, 10], particularly preferably from the interval [2, 8].

[0052] The average distance between adjacent lesions is selected in particular from the interval [1 µm, 10 µm], preferably from the interval [3 µm, 8 µm], and particularly preferably from the interval [5 µm, 7 µm]. The intervals are to be understood as continuous, although one embodiment of the invention may also provide for discrete intervals. The standard deviation of the distances between adjacent lesions is preferably less than 1 µm.

[0053] With these distances, whereby in particular relatively high distances between the individual filaments of > 5 µm, preferably > 7 µm, are provided, the suitable breaking stress can be set by means of filamentation, as can be seen from the series of tests described in more detail below.

[0054] The preference for relatively large spacings is surprising, given that it was previously assumed that the breaking force increases steadily with increasing spacing. However, this relationship has not been borne out, as shown below. It is assumed that the assumption of increasing breaking force only applies again at spacings of more than 8 µm.

[0055] Since this effect, unlike the burst or the burst spacing, also has a positive influence on edge roughness, a large filament spacing is particularly advantageous. In other words, large damage spacing leads to smoother edges. In this respect, choosing larger filament spacing is advantageous. Furthermore, this has a positive effect on speed, as significantly higher cutting speeds can be achieved with lasers of the same frequency.

[0056] In a first more specific embodiment of the invention, the material of the substrate has a thermal expansion coefficient in the interval [3·10 -6< K -1< , 4·10 -6< K -1< ], a modulus of elasticity in the interval [69 kN / mm 2< , 76 kN / mm 2< ] and / or a glass transition temperature in the interval [700°C, 800°C].

[0057] In this first more specific embodiment, the average distance between adjacent lesions is chosen from the interval [6µm, 8µm] and the number of laser pulses to generate each lesion from the interval [7, 9].

[0058] In a second, more specific embodiment of the invention, the material of the substrate has a thermal expansion coefficient in the interval [7·10 -6< K -1< , 8·10 -6< K -1< ], a modulus of elasticity in the interval [69 kN / mm 2< , 76 kN / mm 2< ] and / or a glass transition temperature in the interval [500°C, 600°C].

[0059] In this second, more specific embodiment, the average distance between adjacent lesions is selected from the interval [6 µm, 8 µm] and the number of laser pulses to generate each lesion from the interval [1, 3].

[0060] In a third, more specific embodiment of the invention, the material of the substrate has a thermal expansion coefficient in the interval [3·10 -6< K -1< , 4·10 -6< K -1< ], a modulus of elasticity in the interval [60 kN / mm 2< , 68 kN / mm 2< ] and / or a glass transition temperature in the interval [500°C, 600°C].

[0061] In this third, more specific embodiment, the mean distance between adjacent lesions is either selected from the interval [4µm, 8µm] and the number of laser pulses to generate each lesion from the interval [7, 9] or the mean distance between adjacent lesions is selected from the interval [6µm, 8µm] and the number of laser pulses to generate each lesion from the interval [3, 5].

[0062] Independently of the three aforementioned more specific embodiments and optionally in combination with these more specific embodiments, the substrate may comprise or be made of material of a specific glass type and / or a specific glass composition.

[0063] For example, the substrate may be a lithium aluminosilicate glass with the following composition (in wt%): composition (wt%) SiO2 55-69 Al2O3 18-25 Li2O 3-5 Na2O + K2O 0-30 MgO + CaO + SrO + BaO 0-5 ZnO 0-4 TiO2 0-5 ZrO2 0-5 TiO 2 + ZrO 2 + SnO 2 2-6 P2O5 0-8 F 0-1 B2O3 0-2

[0064] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0065] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 3·10 -6< K -1< and 6·10 -6< K -1< or between 3.3·10 -6< K -1< and 5.7·10 -6< K -1<.

[0066] The lithium aluminosilicate glass preferably has the following composition (in wt%): composition (wt%) SiO2 57-66 Al2O3 18-23 Li2O 3-5 Na2O + K2O 3-25 MgO + CaO + SrO + BaO 1-4 ZnO 0-4 TiO2 0-4 ZrO2 0-5 TiO 2 + ZrO 2 + SnO 2 2-6 P2O5 0-7 F 0-1 B2O3 0-2

[0067] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0068] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 4.5·10 -6< K -1< and 6·10 -6< K -1< or between 4.76·10 -6< K -1< and 5.7·10 -6< K -1<.

[0069] The lithium aluminosilicate glass more preferably has the following composition (in wt%): composition (wt%) SiO2 57-63 Al2O3 18-22 Li2O 3.5-5 Na2O + K2O 5-20 MgO + CaO + SrO + BaO 0-5 ZnO 0-3 TiO2 0-3 ZrO2 0-5 TiO 2 + ZrO 2 + SnO 2 2-5 P2O5 0-5 F 0-1 B2O3 0-2

[0070] Optionally, coloring oxides such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% of As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% of rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0071] In particular, a material of the aforementioned composition can have a thermal expansion coefficient between 4·10 -6< K -1< and 8·10 -6< K -1< or between 5·10 -6< K -1< and 7·10 -6< K -1<. A corresponding glass ceramic can also be provided which has a thermal expansion coefficient between -0.068·10 -6< K -1< and 1.16·10 -6< K -1<.

[0072] In another example, the substrate may be a soda-lime glass having the following composition (in wt%): composition (wt%) SiO2 40-81 Al2O3 0-6 B2O3 0-5 Li 2 O + Na 2 O + K 2 O 5-30 MgO + CaO + SrO + BaO + ZnO 5-30 TiO 2 +ZrO 2 0-7 P2O5 0-2

[0073] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0074] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 5.25·10 -6< K -1< and 10*10 -6< K -1< or between 5.53·10 -6< K -1< and 9.77·10 -6< K -1<.

[0075] The soda-lime glass preferably has the following composition (in wt%): composition (wt%) SiO2 50-81 Al2O3 0-5 B2O3 0-5 Li 2 O + Na 2 O + K 2 O 5-28 MgO + CaO + SrO + BaO + ZnO 5-25 TiO 2 +ZrO 2 0-6 P2O5 0-2

[0076] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0077] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 4.5·10 -6< K -1< and 11·10 -6< K -1< or between 4.94·10 -6< K -1< and 10.25·10 -6< K -1<.

[0078] The soda-lime glass more preferably has the following composition (in wt%): composition (wt%) SiO2 55-76 Al2O3 0-5 B2O3 0-5 Li 2 O + Na 2 O + K 2 O 5-25 MgO + CaO + SrO + BaO + ZnO 5-20 TiO 2 +ZrO 2 0-5 P2O5 0-2

[0079] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0080] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 4.5·10 -6< K -1< and 11·10 -6< K -1< or between 4.93·10 -6< K -1< and 10.25·10 -6< K -1<.

[0081] In another example, the substrate is a borosilicate glass with the following composition (in wt%): composition (wt%) SiO2 60-85 Al2O3 0-10 B2O3 5-20 Li 2 O + Na 2 O + K 2 O 2-16 MgO + CaO + SrO + BaO + ZnO 0-15 TiO2 + ZrO2 0-5 P2O5 0-2

[0082] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0083] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 2.75·10 -6< K -1< and 10·10 -6< K -1< or between 3.0·10 -6< K -1< and 9.01·10 -6< K -1<.

[0084] The borosilicate glass preferably has the following composition (in wt%): composition (wt%) SiO2 63-84 Al2O3 0-8 B2O3 5-18 Li 2 O + Na 2 O + K 2 O 3-14 MgO + CaO + SrO + BaO + ZnO 0-12 TiO2 + ZrO2 0-4 P2O5 0-2

[0085] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0086] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 2.5·10 -6< K -1< and 8·10 -6< K -1< or between 2.8·10 -6< K -1< and 7.5·10 -6< K -1<.

[0087] The borosilicate glass more preferably has the following composition (in wt%): composition (wt%) SiO2 63-83 Al2O3 0-7 B2O3 5-18 Li 2 O + Na 2 O + K 2 O 4-14 MgO + CaO + SrO + BaO + ZnO 0-10 TiO 2 + ZrO 2 0-3 P 2 O 5 0-2

[0088] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0089] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 3.0·10 -6< K -1< and 8·10 -6< K -1< or between 3.18·10 -6< K -1< and 7.5·10 -6< K -1<.

[0090] In another example, the substrate is an alkali metal aluminosilicate glass with the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 40-75 Al 2 O 3 10-30 B 2 O 3 0-20 Li 2 O + Na 2 O + K 2 O 4-30 MgO + CaO + SrO + BaO + ZnO 0-15 TiO 2 + ZrO 2 0-15 P 2 O 5 0-10

[0091] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0092] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 3.0·10 -6< K -1< and 11·10 -6< K -1< or between 3.3·10 -6< K -1< and 10·10 -6< K -1<.

[0093] The alkali metal aluminosilicate glass preferably has the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 50-70 Al 2 O 3 10-27 B 2 O 3 0-18 Li 2 O + Na 2 O + K 2 O 5-28 MgO + CaO + SrO + BaO + ZnO 0-13 TiO 2 + ZrO 2 0-13 P 2 O 5 0-9

[0094] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0095] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 3.75·10 -6< K -1< and 11·10 -6< K -1< or between 3.99·10 -6< K -1< and 10.22·10 -6< K -1<.

[0096] The alkali aluminosilicate glass more preferably has the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 55-68 Al 2 O 3 10-27 B 2 O 3 0-15 Li 2 O + Na 2 O + K 2 O 4-27 MgO + CaO + SrO + BaO + ZnO 0-12 TiO 2 +ZrO 2 0-10 P 2 O 5 0-8

[0097] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0098] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 4.0·10 -6< K -1< and 10·10 -6< K -1< or between 4.5·10 -6< K -1< and 9.08·10 -6< K -1<.

[0099] In another example, the substrate is a low alkali aluminosilicate glass with the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 50-75 Al 2 O 3 7-25 B 2 O 3 0-20 Li 2 O + Na 2 O + K 2 O 0-4 MgO + CaO + SrO + BaO + ZnO 5-25 TiO 2 +ZrO 2 0-10 P 2 O 5 0-5

[0100] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0101] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 2.5·10 -6< K -1< and 7·10 -6< K -1< or between 2.8·10 -6< K -1< and 6.5·10 -6< K -1<.

[0102] The low alkali aluminosilicate glass preferably has the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 52-73 Al 2 O 3 7-23 B 2 O 3 0-18 Li 2 O + Na 2 O + K 2 O 0-4 MgO + CaO + SrO + BaO + ZnO 5-23 TiO 2 +ZrO 2 0-10 P 2 O 5 0-5

[0103] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0104] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 2.5·10 -6< K -1< and 7·10 -6< K -1< or between 2.8·10 -6< K -1< and 6.5·10 -6< K -1<.

[0105] The low alkali aluminosilicate glass more preferably has the following composition (in wt%): Zusammensetzung (Gew.-%) SiO 2 53-71 Al 2 O 3 7-22 B 2 O 3 0-18 Li 2 O + Na 2 O + K 2 O 0-4 MgO + CaO + SrO + BaO + ZnO 5-22 TiO 2 + ZrO 2 0-8 P 2 O 5 0-5

[0106] Optionally, coloring oxides may be added, such as Nd 2 O 3 , Fe 2 O 3 , CoO, NiO, V 2 O 5 , MnO 2 , TiO 2 , CuO, CeO 2 , Cr 2 O 3 , 0 - 2 wt% As 2 O 3 , Sb 2 O 3 , SnO 2 , SO 3 , Cl, F and / or CeO 2 may be added as refining agents, and 0 - 5 wt% rare earth oxides may also be added to introduce magnetic, photonic or optical functions into the glass layer or plate, and the total amount of the overall composition is 100 wt%.

[0107] In particular, a material of the above-mentioned composition may have a thermal expansion coefficient between 2.5·10 -6< K -1< and 7·10 -6< K -1< or between 2.8·10 -6< K -1< and 6.5·10 -6< K -1<.

[0108] The substrate may also have a thickness of less than 350 µm, preferably less than 250 µm, more preferably less than 100 µm, more preferably less than 50 µm, and preferably at least 3 µm, preferably at least 10 µm, more preferably at least 15 µm. Preferred substrate thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm. In particular, the substrate may be formed as a thin glass strip or as a glass film.

[0109] For a better understanding of the invention, a method for separating a substrate, in particular a substrate made of brittle material, especially glass, glass ceramic or silicon, comprising the following method steps is mentioned more generally. a) Providing at least one flat substrate, in particular a glass element, a glass-ceramic element, or a silicon element, with at least one known material characteristic, in particular the thermal expansion coefficient, the elastic modulus, and / or the glass transition temperature, and / or at least one known substrate property, in particular the transmittance, e.g., for laser light, and / or the average roughness R a of at least one of the substrate surfaces. b) Determining at least one process parameter, in particular a damage spacing, a number of laser pulses, and / or a burst frequency, as a function of the at least one known material characteristic and / or the at least one known substrate property. c) Introducing spaced-apart damage along a predetermined dividing line into the flat substrate by means of laser pulses in accordance with the at least one defined process parameter.

[0110] Preferably, the transmission of the substrate, in particular for the pulsed laser beam, can be higher than 70%, preferably higher than 80%, particularly preferably higher than 85%. Furthermore, the average roughness Ra is preferably less than 0.5 µm, preferably less than 0.4 µm, particularly preferably less than 0.35 µm.

[0111] The invention also relates to a workpiece made of glass, glass ceramic and / or silicon, in particular a glass product, a glass ceramic product or a silicon product which is pre-damaged along a parting line, characterized in that the workpiece has damages spaced apart from one another along the parting line and in that the breaking stress σ B for separating the workpiece along the parting line is smaller than a first reference stress σ R1 which is dependent on the respective workpiece and in that the edge strength σ K of the parting edge obtained after the parting is greater than a second reference stress σ R2 which is dependent on the respective workpiece.

[0112] According to the invention, it is provided that (A) both the first and the second reference stress σ R1 = σ R2 are predetermined as a maximum thermal stress σ th which is dependent on the material of the workpiece or, in the case of a chemically or thermally prestressed substrate, as an internal tensile stress σ CT defined by the properties of the prestressed workpiece, wherein in the first case the maximum thermal stress σ th can be determined according to the formula σ th = 0.5·α·E·(T g -100°C), wherein α denotes the thermal expansion coefficient of the material of the workpiece, E denotes the elastic modulus of the material of the workpiece and T g denotes the glass transition temperature of the material of the workpiece and wherein in the second case in the case of a chemically prestressed substrate the internal tensile stress σ CT is determined according to the formula σ CT = (σ CS ·d L ) / (d-2d L ) or in the case of a thermally prestressed substrate according to the formula σ CT = σ CS / 2 can be determined,where σ CS is the surface compressive stress of the prestressed workpiece, d L is the penetration depth of the prestress and d is the thickness of the workpiece, or that (B) for the first reference stress σ R1 ≤ C R1 ·α·E·(T g -100°C) applies and for the second reference stress σ R2 ≥ C R2 ·α ·E·(T g -100°C) applies, where C R1 and C R2 are reference stress coefficients with C R1 =0.5 / k and C R2 =0.5*k and k=1.5, preferably k=2, particularly preferably k=2.5 and where α is the thermal expansion coefficient of the material of the workpiece, E is the elastic modulus of the material of the workpiece and T g is the glass transition temperature of the material of the workpiece. In case (A) it is accordingly provided that both the first and the second reference stress are predetermined as a material the workpiece dependent maximum thermal stress σ R1 = σ R2 = σ th , where the maximum thermal stress σ th can be determined according to the formula σ th = 0.5·α·E·(T g -100°C).,

[0113] In case (B) it is provided that for the first reference voltage σ R1 ≤ C R1 · α ·E·(T g -100°C) and for the second reference voltage σ R2 ≥ C R2 · α ·E·(T g -100°C), where C R1 and C R2 are reference voltage coefficients with C R1 =0.5 / k and C R2 =0.5·k and k=1.5, preferably k=2, particularly preferably k=2.5.

[0114] The workpieces described above are preferably not prestressed. However, a prestressed workpiece, particularly one made of glass, may also be provided.

[0115] In the case of a prestressed workpiece, the first and second reference stresses are intended to be identical and are specified as an internal tensile stress defined by the properties of the prestressed workpiece, i.e., σ R1 = σ R2 = σ CT . In the case of a chemically prestressed workpiece, the internal tensile stress σ CT can be determined using the formula σ CT = (σ CS ·d L ) / (d-2d L ). In the case of a thermally prestressed workpiece, the internal tensile stress σ CT can be determined using the formula σ CT = σ CS / 2.

[0116] Reference is made below to the accompanying figures. In the figures, like reference numerals designate like or corresponding elements.

[0117] They show: Fig. 1: Test results of the fracture stress σ B and edge strength σ K in MPa for SCHOTT AF32 ®< glass with damage along a dividing line for different distances A between adjacent damages and different numbers L of laser pulses to generate each damage, Fig. 2 : Test results of the fracture stress σ B and edge strength σ K in MPa for SCHOTT D263 ®< glass with damage along a dividing line for different distances A between adjacent damages and different numbers L of laser pulses to generate each damage, Fig. 3 : Test results of the fracture stress σ B and edge strength σ K in MPa for SCHOTT BOROFLOAT ®< 33 glass with damage along a dividing line for different distances A between adjacent damages and different numbers L of laser pulses to generate each damage, Fig. 4: Test results of edge roughness in MPa for SCHOTT BOROFLOAT ®< 33 glass with defects along a dividing line for different distances A between adjacent defects and different numbers L of laser pulses to generate each defect, Fig. 5 : a workpiece with two intersecting parting lines, Fig. 6 a workpiece with two groups of intersecting parting lines, Fig. 7 an element cut out of a workpiece, Fig. 8 a variant of the Fig. 6 illustrated embodiment with a web for holding together the workpiece which has been cut into strips, Fig. 9 and Fig. 10 Variants of the Fig. 6 illustrated embodiment with a frame for holding together the workpiece which has been cut into strips, Fig. 11 a workpiece on a carrier, Fig. 12 an embodiment of a workpiece divided into several parts.

[0118] Referring to the Fig. 1 to 3 are the results of a DOE test series for three different glasses, namely SCHOTT AF32 ®< ( Fig. 1 ), SCHOTT D263 ®< ( Fig. 2 ) and SCHOTT BOROFLOAT ®< 33 ( Fig. 3 ) is shown.

[0119] These are just a selection of examples. In general, the invention can be used for various substrates, particularly those made of glass, glass ceramic, and / or silicon with filamentation, and especially for materials with a low thermal expansion coefficient.

[0120] For a large number of samples of these glasses, filamentation was carried out, ie laser pulses were used to introduce spaced-apart damage along a dividing line into the volume of the respective sample.

[0121] For the samples made of SCHOTT AF32 ®< and SCHOTT D263 ®<, substrate thicknesses of approximately 100 µm were chosen, and for the samples made of SCHOTT BOROFLOAT ®< 33, substrate thicknesses of 1 mm were chosen.

[0122] After filamentation, the breaking strength σ B of the glass was tested with respect to the filamented separation line. In other words, the samples were separated along the separation line, and the breaking stress required for separation was measured and recorded. Depending on the material thickness, the 4-point bending strength test method according to DIN EN 843-1 (thicker glasses) or a determination of the breaking strength according to DE 10 2014 110 855 A1 (thinner glasses) was carried out using a stepped roller. DE 10 2014 110 855 A1 describes a method and device for determining the breaking strength of the edges of thin sheets of brittle material.

[0123] In the next step, the strength of the edge obtained after cutting was tested for each sample. To determine the respective edge strength σ K , the samples were tested according to the methods DIN EN 843-1 (thicker glasses) or DE 10 2014 110 855 A1 (thinner glasses), depending on the material thickness. The results were measured and recorded.

[0124] The fracture stresses σ B and edge strengths σ K obtained in this way are shown in the Fig. 1 to 3 plotted on the ordinate axis in units of MPa. The fracture stresses σ B are marked B at the bottom of the diagram, and the edge strengths σ K are marked K accordingly.

[0125] Laser filamentation was also performed using different parameters, meaning samples with different perforations were created. The distances between adjacent damages and the number of laser pulses required to create each damage were varied. These parameters were set for each sample and kept constant during filamentation of a specific sample.

[0126] In the Fig. 1 to 3 The fracture stresses σ B and edge strengths σ K are shown for the various laser filamentation parameters, which are plotted on the abscissa axis. A denotes the distances between adjacent damages in micrometers, and L denotes the number of laser pulses required to create each damage.

[0127] Based on the test results presented, it can be verified that for a cleaving step following filamentation, it is particularly favorable to adjust the process parameters A and L of filamentation with regard to the breaking stress σ B for a separation along the separation line and to the edge strength σ K of the separation edge obtained after separation.

[0128] In particular, the finding that it has proven particularly advantageous to set the breaking stress σ B for separating the glass along the separating line to be smaller than a first reference stress σ R1 which is dependent on the respective glass and the edge strength σ K of the separating edge obtained after the separation to be greater than a second reference stress σ R2 which is dependent on the respective glass can be verified below, wherein, for example, it has proven particularly advantageous if σ R1 = σ R2 = σ th applies, wherein σ th is the maximum thermal stress, which can be assumed, for example, as σ th = 0.5·α·E·(T g -100°C).

[0129] In the Fig. 1 to 3 The maximum thermal stress determined for the respective glass is 0.5· α ·E·(T g -100°C) and is shown as a horizontal line.

[0130] It turns out that this value is the same for all three glasses, ie SCHOTT AF32 ®< ( Fig. 1 ), SCHOTT D263 ®< ( Fig. 2) and SCHOTT BOROFLOAT ®< 33 ( Fig. 3 ), is in the order of magnitude of the measured fracture stresses σ B and edge strengths σ K and that therefore it is possible to select the process parameters A and L in an optimized manner with regard to this value.

[0131] From the Fig. 1 The test results presented, which refer to SCHOTT AF32 ®< glass, show that a damage distance of 7µm in combination with a laser pulse number of 8 is particularly suitable, in particular to minimize the fracture stress σ B with respect to the value 0.5· α ·E·(T g -100°C) and, on the other hand, to maximize the edge strength σ K.

[0132] For the SCHOTT glass D263 ®< Fig. 2 It can be seen that a damage distance of 7µm in combination with a laser pulse number of 2 are particularly suitable parameters.

[0133] Fig. 3For the SCHOTT glass BOROFLOAT ®< 33 it can be seen that either the combination of pulse number 4 and damage distance 7µm or the combination of pulse number 8 and damage distance 5µm or 7µm represent particularly suitable parameters.

[0134] By optimizing the filaments with regard to breaking stress, the subsequent separation process (cleaving step) can be carried out in an optimized manner using thermally induced stresses.

[0135] In particular, the tests show that, surprisingly, perforations with a larger spacing bring advantages in terms of separability across all materials.

[0136] This includes greater process reliability: Even in borderline process windows, i.e. processes with parameter ranges that could not previously be safely managed using the state of the art, the substrates can be safely separated using the method according to the invention.

[0137] In addition, the laser can be operated at reduced power and / or the traversing speed (feed rate) of the laser can be adjusted, particularly increased. For example, for materials with a perforation pitch of 5 µm, the laser power could be reduced from 110 W to 75 W using a process setting with a feed rate of 40 mm / s.

[0138] In an application example, a sample made of SCHOTT BOROFLOAT ®< 33, 1 mm thick, CTE of 3.3·10 -6< K -1< , was filamented with 7 µm spacing of the damages and 6 laser pulses to generate one damage each at 300 kHz and a feed rate of 2100 mm / s.

[0139] A further advantage arises with regard to the shape of the parting edge. Due to the lower stress during the cleaving step, more complex geometries, such as smaller corner radii, can be produced.

[0140] Furthermore, edge quality can be improved: chipping and microcracks are avoided or are neither visually nor microscopically perceptible. This has a particularly positive effect on edge strength.

[0141] In Fig. 4 As an example, the edge roughness for SCHOTT BOROFLOAT®< 33 with a thickness of 1 mm is shown for various process parameters. The number of laser pulses L is denoted by "burst" in this figure. It can be seen that the edge roughness decreases with increasing distance between the damages, even with the same number of laser pulses.

[0142] The following tables list in detail the properties of the Schott glasses AF32 ®< , D263 ®< and BOROFLOAT ®< 33 mentioned above. Table 1: Properties of SCHOTT AF32 ®< : Technical Data: Abmessungen: round and square custom size wafer formats, e.g. 6", 8" or 12" Surface roughness < 1 nm RMS Thicknesses 0.03 mm up to 1.1 mm Standard Thicknesses 0,3 mm, 0,4 mm Luminous transmittance τ n065 (d = 0.5 mm) 91.9 % Coefficient of mean linear thermal expansion α (20 °C; 300 °C) (static measurement) 3.2 · 10 -4< K -1< Transformation temperature Tg 717 °C Dielectric constant ε r at 1MHz 5.1 Refractive index n D 1.5099 Density ρ (annealed at 40 °C / h) 2.43 g / cm 3<

[0143] The elastic modulus of SCHOTT AF32 ®< is estimated at 74.8 kN / mm 2<. Table 2: Properties of SCHOTT glass D263 ®< : Technische Daten Abmessungen 440 mm x 360 mm, other size on request Surface roughness < 1 nm RMS Thicknesses 0.03 mm up to 1.1 mm Standard Thicknesses and packaging units 0.21 mm 100 pcs 0.30 mm 100 pcs 0.40 mm 50 pcs 0.55 mm 50pcs Luminous transmittance τ n065 (d = 0.5 mm) 91.7 % Coefficient of mean linear thermal expansion α (20 °C; 300 °C) (static measurement) 7.2 · 10 -4< K -1< Transformation temperature Tg 557 °C Dielectric constant ε r at 1MHz 6.7 Refractive index n D 1.5230 Density ρ (annealed at 40 °C / h) 2.51 g / cm 3<

[0144] The elastic modulus of SCHOTT D263 ®< is estimated at 72.9 kN / mm 2<.

[0145] The elastic modulus of SCHOTT BOROFLOAT ®< 33 is estimated at 64 kN / mm 2<.

[0146] The problem of a crack not following a predetermined parting line during separation and tearing out, or of the crack not starting or breaking off, is exacerbated when intersecting parting lines are provided. When separating substrates with parting lines consisting of filaments that are arranged at an angle to one another and are separated using thermally induced stress, the problem often arises at the intersection points of the parting lines that crack formation potentially runs in all directions. If the parting lines are used as preparation for fracture as part of a multi-step process (e.g. with the intermediate steps of washing, coating, etc.) for later separation or singulation into several pieces, the pre-processed substrate often has incipient cracks at the intersection points of the parting lines. In this case, the parting lines that are not to be separated until later (e.g. after further process steps such as washing and coating) also have incipient crack formation.This increases the risk that the dividing line will break uncontrollably during further processing.

[0147] In general, in this case too, the invention is particularly suitable for enabling separation along a predetermined line due to the precisely adjusted breaking stress, even if this line is crossed by another separation line with spaced-apart damages. According to a further development of the invention, it is therefore provided that the workpiece machined according to the invention has at least two intersecting separation lines with spaced-apart damages, or that at least two intersecting separation lines with spaced-apart damages are created in the substrate.

[0148] In the case of intersecting parting lines, it is advantageous to provide the workpiece with different parting lines that can be separated with different high voltages.

[0149] In general, without limitation to specific embodiments, a further aspect of the invention therefore provides a workpiece, in particular a glass product, glass ceramic product and / or silicon product, which is pre-damaged along at least two parting lines which intersect, so that the workpiece can be divided by exerting a fracture stress along the parting lines, wherein the fracture stresses for division at the parting or modification lines differ by at least 3 MPa, preferably at least 5 MPa, particularly preferably at least 10 MPa.

[0150] It is particularly advantageous if the main structure of the dividing lines that are to be separated first have a significantly lower tension than those dividing lines that are to be separated later.

[0151] In general, it is preferred that the workpiece again has damages spaced apart along the parting lines, wherein the fracture stress σ B for separating the workpiece along the parting line is less than a first reference stress σ R1 that depends on the respective workpiece, and that the edge strength σ K of the separating edge obtained after separation is greater than a second reference stress σ R2 that depends on the respective workpiece. The fracture stress of the other parting line is then correspondingly at least 3 MPa higher or even lower. This second fracture stress is particularly preferably higher.

[0152] The different fracture stresses can preferably be adjusted by changing the laser parameters, so that all the features of the separating lines created with the ultrashort pulse laser described here also apply to this embodiment with intersecting separating lines. However, it is also conceivable to create damage along the intersecting separating lines in other ways. This embodiment of the invention is therefore not necessarily limited to the introduction of filamentary damage or to laser processing.

[0153] Fig. 5 shows a workpiece or substrate 1 which, as described above, has two parting lines 3, 5. Preferably, the substrate 1 is generally plate-shaped, without limitation to the example shown, and accordingly has two opposite, generally parallel side surfaces 10, 11. With the described method, filament-shaped damage 7 was introduced into the substrate 1 using an ultrashort pulse laser. The laser light is irradiated onto one of the side surfaces 10, 11, so that the filament-shaped damage 7 extends between the two side surfaces 10, 11 following the beam direction. The parting lines 3, 5 intersect at right angles in the example shown, as is also preferred in order to separate rectangular parts.

[0154] As shown by Fig. 5 As can be seen, the distances a1, a2 of the filamentary damage 7 along the dividing lines 3, 5 differ. In the example shown, the distance a1 of the filamentary damage along the dividing line 3 is smaller than the distance a2 of the filamentary damage along the dividing line 5. This means that the breaking stress σ B1 for a separation at the dividing line 3 is different from the breaking stress σ B2 for the separation at the dividing line 5. In accordance with the observation explained above, the breaking stress for the dividing line 3 can be higher or lower due to the smaller distance a1. Typically, a minimum of the breaking stress is observed at a distance between the filament lines in the range of 5 to 7 µm.In general, without limitation to the example shown, a workpiece or a substrate 1 is provided in which the distances of the filament-shaped damages differ, wherein the distances are smaller at one of the dividing lines 3 than at the other of the intersecting dividing lines.

[0155] In a further embodiment, the workpiece or substrate 1 is characterized by at least two different parting lines as in Fig. 5 shown, wherein the breaking stress σ B1 for separating the workpiece 1 along a separating line 3 is smaller than a first reference stress σ R1 which is dependent on the respective workpiece, wherein the edge strength σ K of the separating edge obtained after separating is greater than a second reference stress σ R2 which is dependent on the respective workpiece, and wherein the second separating line 5 has a significantly higher breaking stress of at least σ B1 + 5MPa, preferably σ B1 + 10 MPa, preferably σ B1 + 15MPa. Preferably, the second separating line is even so pronounced that its associated breaking stress is above σ R1.

[0156] In a further embodiment, the substrate is provided with a plurality of separating lines for subsequent separation, wherein separating lines of the same direction are also generated with the same laser process parameters and thus have the same breaking stresses, and only different breaking stresses exist between separating lines of different directions. In other words, more than two intersecting separating lines are provided, wherein the set of separating lines can be subdivided into at least two groups of adjacent separating lines, wherein the average breaking force of the separating lines of one group deviates from the average breaking force of another group by the above-mentioned value of at least 3 MPa. An example of such a workpiece or substrate 1 shows Fig. 6 . Several dividing lines 3 run parallel to each other and thus next to each other along the side surface 10. These dividing lines 3 are crossed by dividing lines 5 which also run parallel to each other. As in the Fig. 5 In the example shown, the dividing lines 3, 5 intersect at right angles. The set of parallel dividing lines 3 forms a first group 30 of dividing lines, and the dividing lines 5 running perpendicular to them form a further group 50. Groups 30, 50 are characterized by the fact that their dividing lines each have filament-shaped damage 7 that is equally spaced apart but at different distances from a dividing line of the other group. Therefore, the breaking stresses of the dividing lines 3 of group 30 also have a value σ B1 that differs from the value σ B2 of the dividing lines 5 of the further group 50.

[0157] In principle, there are several ways to change or adjust the breaking stress along a dividing line. For example, the number of burst pulses used to form the filament can be varied (in the range 1-100 pulses, preferably in the range 2-20 pulses). The pulse energy of the single or burst pulse can also be varied in the range from 100 µJ to 1 mJ for single pulses or 400 µJ to 4 mJ for burst pulses. Furthermore, as shown in the figures, the distance between the filaments 7 within the individual dividing lines 3, 5 can be varied to different values ​​in the range from 1 µm to 25 µm, particularly preferably in the range from 2 µm to 20 µm, resulting in different distance values ​​a 1 and a 2.

[0158] For example, for a 0.5 mm thick alkali boroaluminosilicate glass, a system of separation lines with different fracture stresses can be created by varying the burst energy from 300 µJ to 400 µJ, reducing the refractive power from 25 MPa to approximately 15 MPa (using a USP laser with a repetition rate of 100 kHz and a 10 ps pulse duration). Furthermore, increasing the pitch distance leads to a decrease in the required fracture stress for the separation process by approximately 5 MPa: With a pitch of 5 µm between the introduced modifications, a glass as described above results in a fracture stress of approximately 45 MPa, while the fracture stress at a distance of 10 µm is only 15 MPa.

[0159] After introducing the separation lines, the substrate 1 can be separated in a two-step separation process, first by breaking along the first direction and then by breaking along the second direction. In this case, the adjacent edges of the sections have differently spaced periodic structures (by opening the filament channel into two cylinder halves), which are accessible to common topological measurement methods such as tactile or optical profilometry or electron microscopy. A corresponding element 2 cut out of the workpiece 1 is shown in Fig. 7 shown.

[0160] As can be seen from the schematic representation, a disc-shaped glass or glass-ceramic element 2 is provided which has two opposite side surfaces 10, 11 and edge surfaces 13, 14, 15, 16, wherein at least two of the edge surfaces 13, 14, 15, 16 have filament-shaped damages 7 which run at a periodic spacing next to one another in the direction from one of the side surfaces 10, 11 to the other of the side surfaces on the edge surface, wherein the period of the spacing of the filament-shaped damages differs from one another on at least two of the edge surfaces 13, 14, 15, 16.

[0161] As in the example shown, a generally quadrangular shape is preferred, so that the element 2 has two pairs of opposite edge surfaces 13, 15 and 14, 16. The period of the filamentary damage 7 is preferably the same for each pair of opposite edges. Regarding the periods or spacing of the filamentary damage, the thickness of the element 2, and its material, all information disclosed here regarding the method according to the invention and the workpiece that can be produced thereby applies accordingly.

[0162] Without limitation of generality, the separation can be carried out by a mechanical breaking process or a laser-based thermal separation process (using CO2 laser) or other methods.

[0163] In a further embodiment, the individual strips (formed by opposing edges of equal breaking stress) remain connected to each other via a common web, which can be used as a handling aid for subsequent process steps such as washing, coating, and subsequent separation. An exemplary embodiment of such a workpiece 1 shows Fig. 8 . As can be seen from the exemplary figure, the parting lines 5 of one of the groups 50 end before one of the edges of the workpiece 1, so that a web 18 is formed between the ends of the parting lines 5 and the edge 20 of the workpiece, to which detachable elements 2 remain attached, even if the workpiece 1 is separated at the parting lines 5 ending before the edge 20.

[0164] In a further embodiment, the workpiece 1 prepared for separation has a surrounding frame from which entire strips or individual pieces can be broken off during separation. This embodiment with a frame 22 shows Fig. 9 During the separation process, the handling frame can be retained as a whole or disassembled step by step. As with the web 18 of the embodiment according to Fig. 8 the dividing lines of one of the groups end before the edge 20 of the workpiece 1. In the case of a frame 22, this then applies to both groups 30, 50.

[0165] Other variants, in which the filamented separating lines partially extend into the handling frame or handling strip, are also conceivable. An example of this is shown in Fig. 10 . In this example, one side of the frame 22 is determined by the distance of the ends of the dividing lines 5 to the edge 20, while the other sides of the frame are limited by the long sides of the dividing lines 3, 5.

[0166] Fig. 11 shows an example of how to handle a workpiece 1 according to the invention, for example, for further industrial processing, while avoiding premature separation at the parting lines 3, 5. In this example, the workpiece 1 is attached to a carrier 24 by one of its side surfaces 11. The carrier 24 can be, for example, a glass or silicon wafer or a polymer or a plastic plate.

[0167] In the design of the Fig. 6 The spacing of the filamentary damages 7 and the fracture stresses are different in groups, wherein the groups are formed by adjacent and non-intersecting dividing lines. This does not preclude providing one or more of the adjacent dividing lines with a different, in particular lower, fracture stress. Thus, according to a further embodiment, the substrate or workpiece 1 is divided into several larger sections by a suitable choice of the fracture stresses, which can themselves be disassembled again. This subdivision does not have to be an actual separation, but is to be understood in particular as a subdivision of the workpiece at the dividing lines between the sections. Fig. 12 In the example shown, the workpiece 1 is divided into two sections 8, 9 at a dividing line 6.

[0168] For example, only every nth parallel dividing line has the same breaking stress, and the dividing lines in between have a different breaking stress value. In this case, any combination of parallel and perpendicular dividing lines is possible. The breaking stresses can be varied in each case - as mentioned above - by changing the pulse energy, burst number, or spacing of the introduced modifications. A subdivision in which the dividing line at the boundary between the sections has a higher breaking stress than neighboring dividing lines would be conceivable. In order to enable separation first into the sections 8, 9 and then further into individual elements 2, it is particularly preferred to set a lower breaking stress for the dividing line(s) 6 than for the neighboring dividing lines within the sections 8, 9.According to this embodiment of the invention, the workpiece 1 has a plurality of parting lines 5, 6 running alongside one another, with at least one of the parting lines 6 running between two adjacent parting lines 5, and with the parting line running between the two adjacent parting lines 5 having a lower breaking stress than the adjacent parting lines 5. Preferably, as in the example shown, two groups of parting lines 5 with higher breaking stress run on either side of the parting line 6 with the lower breaking stress. The difference in the breaking stresses can generally be selected in the same way as in the embodiments with intersecting parting lines, i.e. preferably at least 3 MPa, in particular at least 5 MPa.

[0169] All workpieces described here can, in principle, also be coated substrates. The coating can, if necessary, also be applied before the laser-assisted insertion of the dividing lines. According to one embodiment of the invention, an organic functional coating for protein or DNA analyses can be applied as the coating. This allows the workpiece 1 or an element 2 that can be separated from the workpiece 1 to be used as a DNA or protein microarray. Suitable coatings for this purpose are aminosilanes, epoxysilanes, aldehydesilanes, hydrogels, streptavidin, and certain polymers. The coating can then be provided with a microarray of oligonucleotides, cDNA / PCR, BAC (Bacterial Artificial Chromosomes), peptides, proteins, antibodies, glycans, or cell or tissue samples. The samples can be prepared together in this way and then, after separation, examined and / or shipped separately. Bezugszeichenliste:

[0170] 1Workpiece 2Element 3, 5, 6Parting line 7Filament-shaped damage 8, 9Parts of 1 10, 11Side surfaces of 1 30, 50Groups of parting lines 13, 14, 15, 16Edge surface 18Web 20Edge of 1 22Frame 24Beam

Claims

1. A method for separating a substrate (1) made of glass, glass ceramic and / or silicon, wherein defects are introduced at a distance from one another into the substrate along a predetermined separation line using at least one pulsed laser beam, the material of the substrate being transparent to the laser pulses; wherein both the average spacing between adjacent defects and the number of laser pulses for producing a respective defect are selected such that a) the breaking stress σB for separating the substrate (1) along the separation line is smaller than a first reference stress σR1 which depends on the respective substrate; that b) the edge strength σk of the separation edge obtained after separation is greater than a second reference stress σR2 which depends on the respective substrate; and that c) the substrate can be separated after the defects have been introduced by applying a stress along the separation line; and wherein the first and the second reference stresses are identical, σR1 = σR2 and are specified as a maximum thermal stress σth which depends on the material of the substrate; or in the case of a chemically or thermally toughened substrate as an internal tensile stress σCT defined by the properties of the toughened substrate; wherein in the first case, the maximum thermal stress σth can be determined according to the formula σth = 0.5·α·E·(Tg - 100 °C), wherein α denotes the coefficient of thermal expansion of the material of the substrate, E denotes the Young's modulus of the material of the substrate, and Tg denotes the glass transition temperature of the material of the substrate; and wherein in the second case the internal tensile stress σCT can be determined for a chemically toughened substrate according to the formula σCT = (σCS·dL) / (d - 2dL), or for a thermally toughened substrate according to the formula σCT = σCS / 2, wherein σCS is the surface compressive stress of the toughened substrate, dL is the penetration depth of the preliminary stress, and d is the thickness of the substrate; or wherein σR1 ≤ CR1·α·E·(Tg - 100 °C) applies for the first reference stress, and σR2 ≥ CR2·α·E·(Tg - 100 °C) applies for the second reference stress, wherein CR1 and CR2 are reference stress coefficients with CR1 = 0.5 / k and CR2 = 0.5·k and k = 1.5, preferably k = 2, most preferably k = 2.5, and wherein α denotes the coefficient of thermal expansion of the material of the substrate, E denotes the Young's modulus of the material of the substrate, and Tg denotes the glass transition temperature of the material of the substrate.

2. The method according to the preceding claim, wherein once the defects have been introduced, a point of incidence of a laser radiation, preferably from a CO2 laser, is moved over the substrate along the separation line in order to induce the stress to be applied for the separation along the separation line.

3. The method according to any one of the preceding claims, wherein the average spacing between adjacent defects is selected from the interval of [1 µm, 10 µm], preferably selected from the interval of [3 µm, 8 µm], most preferably selected from the interval of [5 µm, 7 µm]; and / or wherein the number of laser pulses for generating a respective defect is selected from the interval of [1, 20], preferably selected from the interval of [1, 10], most preferably selected from the interval of [2, 8].

4. A workpiece made of glass, glass ceramic and / or silicon, which is pre-damaged along a separation line, characterized in that the workpiece includes defects that are spaced apart from one another along the separation line; and that the breaking stress σB for separating the workpiece along the separation line is smaller than a first reference stress σR1 which depends on the respective workpiece; and that the edge strength σK of the separation edge obtained after separation is greater than a second reference stress σR2 which depends on the respective workpiece; wherein both the first and second reference stresses, σR1 = σR2, are specified as a maximum thermal stress σth which depends on the material of the workpiece; or in the case of a chemically or thermally toughened substrate as an internal tensile stress σCT defined by the properties of the toughened workpiece; wherein in the first case the maximum thermal stress σth can be determined according to the formula σth = 0.5·α·E·(Tg - 100°C), wherein α denotes the coefficient of thermal expansion of the material of the workpiece, E denotes the Young's modulus of the material of the workpiece, and Tg denotes the glass transition temperature of the material of the workpiece; and wherein in the second case the internal tensile stress σCT can be determined for a chemically toughened substrate according to the formula σCT = (σCS·dL) / (d - 2dL), or for a thermally toughened substrate according to the formula σCT = σCS / 2, wherein σCS is the surface compressive stress of the toughened workpiece, dL is the penetration depth of the preliminary stress, and d is the thickness of the workpiece; or wherein σR1 ≤ CR1·α·E·(Tg - 100 °C) applies for the first reference stress, and σR2 ≥ CR2·α·E·(Tg - 100 °C) applies for the second reference stress, wherein CR1 and CR2 are reference stress coefficients with CR1 = 0.5 / k and CR2 = 0.5·k and k = 1.5, preferably k = 2, most preferably k = 2.5, and wherein α denotes the coefficient of thermal expansion of the material of the workpiece, E denotes the Young's modulus of the material of the workpiece, and Tg denotes the glass transition temperature of the material of the workpiece.

5. The workpiece according to claim 4, characterized in that the workpiece has at least two intersecting separation lines (3, 5) comprising defects (7) that are spaced apart from one another.

6. The workpiece according to the preceding claim, wherein the breaking stresses for separating along the separation lines differ by at least 3 MPa, preferably by at least 5 MPa, most preferably by at least 10 MPa.

7. The workpiece according to any one of the two preceding claims, wherein the spacings between the filament-shaped defects (7) differ, wherein one of the separation lines (3) features spacings that are smaller than that of the other of the intersecting separation lines (3, 5).

8. The workpiece according to any one of the three preceding claims, which includes more than two intersecting separation lines, wherein the plurality of separation lines can be subdivided into at least two sets (30, 50) of separation lines (3, 5) running next to one another, wherein the average breaking force for the separation lines of one set differs from the average breaking force for another set by at least 3 MPa.

9. The workpiece according to the preceding claim, characterized in that the separation lines (5) of one of the sets terminate before one of the edges of the workpiece (1), so that a web (18) or frame (22) is defined between the ends of the separation lines (5) and the edge (20) of the workpiece (1), where separable elements (2) remain attached even when the workpiece (1) is severed along the separation lines (5) that terminate before the edge (20).

10. The workpiece (1) according to any one of claims 4 to 9, provided in the form of a coated substrate, preferably coated with an organic functional coating for protein or DNA analyses.