Electric heating – Metal heating – By arc
Reexamination Certificate
1999-01-29
2001-07-10
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
C219S121670, C219S121760, C219S121770
Reexamination Certificate
active
06259058
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention generally relates to the physical separation of a non-metallic substrate into a plurality of smaller substrate pieces. In particular, the invention relates to a method and apparatus for splitting a non-metallic substrate by the process of micro-cracking and controlled propagation.
BACKGROUND OF THE INVENTION
Many products made from a brittle non-metallic material, for example glass and semi-conductor wafer materials, are formed by separating a piece, sheet, wafer, or panel into a number of smaller pieces of the desired size or sizes. For example, many glass products are formed by a large sheet of glass separated into smaller pieces of the desired size. The most common method for cutting these sheets and other substrates includes the use of mechanical cutting tools. For example, glass sheets have been cut by scribing the glass with a diamond-tipped scribe or a carbide wheel to weaken the molecular structure. After the scribe has been made, physical pressure is applied to create a force at the scribe line to hopefully break the glass along the scribe line.
However, cutting with mechanical tools has significant disadvantages. One significant disadvantage is the inability to obtain smooth edges. This may be unacceptable for many products because of the required quality of the edge faces. Accordingly, as an attempt to rectify this drawback, secondary steps such as grinding, edge seaming, and polishing may be performed. However, such secondary steps slow down the manufacturing process and can be expensive. Another disadvantage is that edge defects on some of these rough edges may result in crack propagation during further processing or in the ultimate product. The edge strength of the substrate is also reduced by this process. Yet another disadvantage is the creation of glass particulates and “shards” during the cutting stage. These glass shards and particulate are undesirable because they can contaminate the substrate being separated, and require that additional clean-up steps be performed to minimize their impact on the manufacturing process. Mechanical tools also create wide scribe lines which are undesirable because the process reduces the useful area of the substrate from which the parts are cut. Further, mechanical tools are subject to wear, and worn tools result in inconsistent and unreliable cuts.
One alternative to mechanical division of pieces of non-metallic brittle substrates is using a laser to melt the substrate along a predetermined line. European Patent Application No. 82301675.3 discloses one such method. According to this method, a sheet of glass is mounted to a plate. A high-powered laser beam is applied to cause rapid localized heating of the glass in a small heat affected zone that extends through the entire thickness of the glass. This heats the glass above its annealing temperature so that part of the glass is vaporized and part of the glass becomes viscous. A pressurized air jet removes the molten glass from the heat affected zone to divide the glass substrate. However, this process also suffers from drawbacks.
A drawback of this process is that predictable and highly accurate cuts are unobtainable because the glass is subjected to extreme temperatures and is removed from the cutting line. This lack of precision is magnified with thicker pieces of glass. Additionally, secondary steps such as grinding, edge seaming, and polishing may also need to be performed to achieve desired edge face quality.
Another alternative to mechanical cutting of pieces of non-metallic brittle materials has been the process of creating a localized fracture through a substrate, and propagating the localized fracture to part the substrate. On such method is disclosed in U.S. Pat. No. 3,629,545 to Graham et al. According to this process, light from a laser is focused by a lens system upon the upper surface of the substrate at an extreme edge of the substrate. The lens system is adjusted so that the focal point of the laser beam image falls precisely at the upper surface of the substrate. The concentrated laser energy creates a localized fracture in the substrate. The substrate is moved relative to the beam. This relative movement propagates the initial localized fracture along a desired partition path. There have been many variations to this process.
The processes of creating a localized fracture and propagating the fracture have also suffered drawbacks. One drawback is that these processes include inefficiencies rendering them impractical and/or ineffective for many commercial applications. For example, some of these processes are limited by cutting speed. Further, some of these processes still require manual breakage of the substrate after the passage of the laser. Another drawback to these processes is the inherent limitations imparted due to the coefficient of thermal expansion of the substrate being cut.
Therefore, there exists a need for an improved method of dividing or parting substrates of brittle non-metallic material that overcomes these and other problems.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus that separates non-metallic substrates by microcracking which overcomes the drawbacks of the prior art. Thus, objects of the present invention include features enabling the apparatus to make the process easily adaptable for many applications, achieve fast cutting speeds and total separation of the substrate, and eliminate the need for secondary operations.
It is an object of the present invention to include a unique beam arrangement to obtain controlled separation with fast separation speeds.
It is an object of the present invention to provide an apparatus for separating a non-metallic substrate by propagating a microcrack having a laser, optical elements, and a quenching device. The laser generates and emits an incident beam of coherent radiation having a Gaussian energy distribution profile. Optical elements are positioned in the path of the beam and alter the energy distribution profile by imparting spherical aberration thereto. The optical elements also direct at least a portion of the beam with the altered energy distribution profile onto the substrate. The quenching device projects a coolant stream onto the substrate to promote microcracking of the substrate.
In another object of the present invention to provide, an apparatus is used for separating a non-metallic substrate by propagating a microcrack. The apparatus includes a laser, a splitting device, and a quenching device. The laser generates a single incident source beam of coherent radiation. The splitting device is positioned in the path of at least a part of the source beam and splits a portion of the source beam into a plurality of beams directable onto the substrate to impinge at distinct spots. The quenching device imparts a coolant stream onto the substrate.
It is another object of the present invention to provide an apparatus having a first beam, a quenching device, a second beam, and a moving device. The first beam impinges on the substrate at a first spot that has a leading end and a trailing end. The quenching device is positioned so that a coolant stream may be applied to the substrate at or immediately adjacent to the trailing end of the first spot. The second beam impinges on the substrate at a second spot that is located behind the first spot. The moving device moves the first and second beams and the coolant stream relative to the substrate. The apparatus is used for separating a non-metallic substrate along a separation line by propagating a microcrack.
In yet another object of the present invention, an apparatus is used for separating a non-metallic substrate by propagating a microcrack. The apparatus has an incident beam of coherent radiation that impinge on the substrate, a source of pressurized helium, a nozzle fluidly coupled to the source of helium, and an arrangement for moving the beam and the coolant stream relative to the substrate. The nozzle is positioned to project a coolant stream of helium from
Accudyne Display and Semiconductor Systems, Inc.
Banner & Witcoff , Ltd.
Dunn Tom
Johnson Jonathan
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