Patent Application
20130193617
This disclosure relates to separating non-metallic materials into a plurality of smaller pieces. In particular, this disclosure is directed to using a single laser source to generate a scribe beam and a break beam for use with a cooling source to separate glass, silicon, ceramic, or other non-metallic materials.
High-power lasers (e.g., 500 W CO2 lasers) may cut through non-metallic substrates such as glass, silicon, or ceramic by melting, evaporation, and ejection of material, which leads to poor surface integrity, wide tolerances, and degraded strength. Other methods for separating a non-metallic material use a non-melting (or non-evaporation) thermal process followed by a strain process. For the thermal process, any brittle material exceeds its critical thermal shock temperature when its temperature is elevated to a desired level and then rapidly cooled or quenched to break its molecular bonds. This forms a “vent” or “blind crack” in the material. Certain thermal processes use a first laser source to generate a first laser beam that heats the material along a scribe line. The first laser beam may be closely followed by a cooling stream of fluid (e.g., Helium and/or water) for quenching.
The strain process may then be used to completely separate the material by breaking the material along the blind crack using either traditional mechanical methods or a second laser process. Mechanical strain may include, for example, using a “guillotine” breaker to apply sufficient physical force to a thin substrate (e.g., less than about 0.5 mm) so as to completely break the substrate along the scribe line. For thicker material, however, the residual tensile forces resulting from the laser scribing operation may not be sufficient to cleanly separate the material using mechanical force. Thus, a second laser source may be used to generate a second laser beam to rapidly reheat the substrate along the scribe line, following the quenching step, to fully separate the material. Using two lasers, however, increases system complexity and maintenance.
A non-metallic material is separated using a single laser beam that is converted into a scribe beam and a break beam. A system includes a single laser source for generating a laser beam and a beam separator for converting the laser beam into a scribe beam having a first average power and a break beam having second average power. The beam separator directs the scribe beam along a first path to a scribe line on a non-metallic substrate and the break beam along a second path to the non-metallic substrate at a location that is spaced apart from the scribe beam. The scribe beam rapidly heats the non-metallic substrate along the scribe line. A quenching subsystem applies a stream of cooling fluid to the non-metallic substrate to propagate a microcrack along the scribe line heated by the scribe beam. The break beam rapidly reheats the non-metallic substrate quenched by the stream of cooling fluid to separate the non-metallic substrate along the microcrack.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.
Systems and methods separate a non-metallic material by converting a laser beam from a single laser source into a scribe beam and a break beam. By way of example, and not by limitation, the non-metallic material may include glass, silicon, ceramic, or other material. The average power of the scribe beam is selected so as to propagate, in cooperation with a cooling stream, a microcrack along a desired scribe line in the non-metallic material, without substantially ablating (e.g., melting, evaporating, and/or ejecting) the material. The average power of the break beam is selected to produce a tensile force along the scribe line so as to break the material into separate pieces.
In one embodiment, a continuous wave (CW) laser beam is “time-shared” between the scribe beam and the break beam using, for example, a fast steering mirror (FSM), a mirror galvanometer beam deflector (referred to herein as a “galvo” or “galvo mirror”), an acousto-optic deflector (AOD), an electro-optic deflector (EOD), other optical deflection devices, or a combination of the foregoing. In such embodiments, the CW beam is deflected along a scribing beam path during certain time periods and along a breaking beam path during other time periods. As discussed below, the average powers of the respective beams may be controlled by selecting duty cycles for the scribe beam and the break beam.
In addition, or in other embodiments, the respective average powers may be controlled by selectively modulating the scribe beam and the break beam. For example, as discussed in detail below, an acousto-optic modulator (AOM) may receive the CW beam and output both (e.g., as a 0th order beam and a 1st order beam) a modulated scribe beam and a modulated break beam.
The average power of the scribe beam is selected to heat the material with little or no ablation, and to keep the surface temperature of the material (e.g., glass) below the “transition” temperature to avoid damaging the integrity of the material. Once a quenching jet is applied, the surface of the glass contracts while the center is still under expansion, which results in large surface tensile stress. When such tensile stress exceeds the critical breaking point of glass, a vent is created which follows the path defined by the scribe beam and the cooling nozzle. Depending on the material, a cooling liquid jet, a mix of liquid and gas, or even gas alone may be used for quenching. For certain materials, such as those with low thermal expansion coefficients, a high gradient may be required to exceed the critical breaking stress. In such embodiments, a gas/water mixture may be used for effective quenching. In other words, latent heat released from the evaporation of the liquid is combined with convective and conductive heat transfer and serves to quench the material in a more efficient manner, thereby providing fast temperature quenching and creating a large thermal gradient for high tensile stress.
In certain embodiments, an initial defect, e.g., a notch on the edge or a small crack, may be required to propagate a microcrack through a material. Many materials already have defects positioned along their edges as result of previous manufacturing processes. It has been found more desirable, however, to introduce an initiation defect in a controlled manner at a given location rather than to rely on residual defects.
Reference is now made to the figures in which like reference numerals refer to like elements. For clarity, the first digit of a reference numeral indicates the figure number in which the corresponding element is first used. In the following description, numerous specific details are provided for a thorough understanding of the embodiments disclosed herein. However, those skilled in the art will recognize that the embodiments can be practiced without one or more of the specific details, or with other methods, components, or materials. Further, in some cases, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the invention. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Embodiments may include various steps, which may be embodied in machine-executable instructions to be executed by a general-purpose or special-purpose computer (or other electronic device). Alternatively, the steps may be performed by hardware components that include specific logic for performing the steps or by a combination of hardware, software, and/or firmware.
Embodiments may also be provided as a computer program product including a non-transitory, machine-readable medium having stored thereon instructions that may be used to program a computer (or other electronic device) to perform the processes described herein. The machine-readable medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, CD-ROMs, DVD-ROMs, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, solid-state memory devices, or other types of media/computer-readable medium suitable for storing electronic instructions.
As shown in
For illustrative purposes, the scribe beam 124 is shown with a solid line and the break beam 126 is shown with a dashed line. In this embodiment, the steerable deflector 114 time-shares the laser beam 122 between the two paths. By way of example, time-sharing may result in the 750 W laser beam 122 being divided such that the scribe beam 124 has an average power of about 250 W and the break beam 126 has an average power of about 500 W. Skilled persons will recognize, however, that the power of the laser beam 122 may be distributed in any way between the scribe beam 124 and the break beam 126, depending on the particular material being separated and the particular laser processing application, including distributing more power to the scribe beam 124 than to the break beam 126. In certain embodiments, parameters (e.g., spot size or shape) of the scribe beam 124 and the break beam 126 may be selectively and separately controlled by additional optical elements (not shown) in the respective scribing and breaking beam paths.
Returning to
For example,
In other embodiments, the steerable deflector 114 is configured to deflect in two directions (e.g., in both an X-axis direction and a Y-axis direction). For example, the steerable deflector 114 may include a first FSM to deflect in the X-axis and a second FSM to deflect in the Y-axis. Other configurations are also possible such as an FSM to deflect in a first direction and a galvo to deflect in a second direction. Thus, the steerable deflector 114 may deflect one or both of the beams 124, 126 in a direction that is perpendicular to the scribe line 316.
For example,
The system 500 also includes a relay lens 512 and a deflector 514 for directing the scribe and break beams 124, 126 along their respective paths to the material 110. In one embodiment, the deflector 514 comprises a fixed mirror. In other embodiments, the deflector 514 is a steerable deflector and may include, for example, one or more FSM and/or one or more galvo. In addition, or in other embodiments, the AOD may include a plurality of AODs and/or EODs for selectively deflecting at least one of the scribe beam 124 and the break beam 126 in at least two directions (e.g., in the X-axis direction and the Y-axis direction), as discussed above.
In certain embodiments, parameters of the scribe beam 124 and the break beam 126 may be selectively and separately controlled. For example, the optic elements 612(a), 612(b) in each path, which are optional, may be included to shape or change the optical properties of the beams and may include, for example, polarizers, polarization modifiers, faraday isolators, spatial beam profile modifiers, temporal beam profile modifiers, frequency shifters, frequency-multiplying optics, attenuators, pulse amplifiers, mode-selecting optics, beam expanders, lenses, and relay lenses. Additional optic elements may also include delay elements that include an extra optical path distance, folded optical paths, and fiber-optic delay lines.
It will be understood by those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.
