Electric heating – Metal heating – By arc
Reexamination Certificate
2002-09-23
2004-04-13
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121620, C219S121670, C219S121700, C219S121750, C219S121770, C219S121810
Reexamination Certificate
active
06720519
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to material ablation with pulsed light sources and particularly relates to laser drilling and laser milling.
BACKGROUND OF THE INVENTION
Material ablation by pulsed light sources has been studied since the invention of the laser. Reports in 1982 of polymers having been etched by ultraviolet (UV) excimer laser radiation stimulated widespread investigations of the process for micromachining. Since then, scientific and industrial research in this field has proliferated—mostly spurred by the remarkably small features that can be drilled, milled, and replicated through the use of lasers.
Ultrafast lasers generate intense laser pulses with durations from roughly 10
−11
seconds (10 picoseconds) to 10
−14
seconds (10 femtoseconds). Short pulse lasers generate intense laser pulses with durations from roughly 10
−10
seconds (100 picoseconds) to 10
−11
seconds (10 picoseconds). A wide variety of potential applications for ultrafast lasers in medicine, chemistry, and communications are being developed and implemented. These lasers are also a useful tool for milling or drilling holes in a wide range of materials. Hole sizes as small as a few microns, even sub-microns, can readily be drilled. High aspect ratio holes can be drilled in hard materials, such as cooling channels in turbine blades, nozzles in ink-jet printers, or via holes in printed circuit boards.
The ability to drill holes as small as microns in diameter is a basic requirement in many high-tech manufacturing industries. The combination of high resolution, accuracy, speed, and flexibility has allowed laser processing to gain acceptance in many industries, including the manufacture of integrated circuits, hard disks, printing devices, displays, interconnects, and telecommunication devices. The need remains, however, for a system and method of laser drilling that solves several problems that continue to exist in the field of material ablation with pulsed light sources.
One problem that continues to exist in the field of material ablation with pulsed light sources relates to use of ultrafast lasers for parallel material ablation to address spectral dispersion issues. Due to the large spectral bandwidth of femtosecond laser sources, there can be problems if one attempts to use femtosecond laser pulses with a diffractive optical element (DOE) as a beamsplitter for parallel processing, e.g., drilling multiple holes simultaneously. This is because the DOE is spectrally dispersive which can cause focus distortion, often severely. This drawback reduces its utility as a commercial manufacturing tool. What is needed is a way to use ultrafast lasers for parallel material ablation to address spectral dispersion issues.
Another problem that continues to exist in the field of material ablation with pulsed light sources relates to control of thermal effects during ablation to improve the quality and repeatability of the holes drilled. Most current drilling techniques perform laser drilling with long pulse, high-energy lasers. The thermal effects that occur when these techniques are used cause the shape of the workpiece holes drilled to be unpredictable and not repeatable. What is needed is a way to control thermal effects during ablation to improve the quality and repeatability of the holes drilled.
Another problem that continues to exist in the field of material ablation with pulsed light sources relates to control drilling precision and the resulting hole shape during laser ablation. For many applications, such as inkjet printer nozzle holes, customers require that holes be drilled having a tapered shape where the input end of the hole is wider than the exit hole. The measurements of the hole (input diameter, exit diameter, and taper) are critical to the product quality and the operation of the end application. For example, the taper of a drilled hole controls the fluid dynamics of an inkjet printer nozzle. The hole measurements for a given product could vary widely and require the ability to adjust for a specific end application. What is needed is a way to control drilling precision and the resulting hole shape during laser ablation.
Another problem that continues to exist in the field of material ablation with pulsed light sources relates to performing parallel drilling of tapered holes. Current methods of laser drilling use excimer lasers to drill tapered holes. Excimer lasers are generally not used with diffractive optical elements as beamsplitters due to the poor spatial beam quality of the excimer laser. Parallel processing with excimer lasers normally require masking techniques to accomplish drilling of multiple holes, which significantly reduces utilization efficiency of the laser light. On the other hand, laser sources with high spatial beam quality can be focused to small beam spots without the use of projection imaging a mask onto the work piece. What is needed is a way to perform parallel drilling of tapered holes.
Another problem that continues to exist in the field of material ablation with pulsed light sources relates to performing high quality laser drilling with metal foils while minimizing thermal effects. Current methods of laser drilling use excimer lasers to drill holes in polymeric materials. Excimer lasers are generally not conducive to drilling high quality holes in metal foils because the long-duration (nanoseconds) excimer pulses can have significant melting in metal foils that leads to poor quality of the holes. What is needed is a way to perform high quality laser drilling with metal foils while minimizing thermal effects.
Parallel processing of laser-milled holes is key to increasing the throughput of, and thus the profitability of laser micromachining. Beam splitting devices such as diffractive optical elements (DOEs) are currently used in laser micromachining to divide a single beam into multiple beams to allow parallel processing. However, hole geometry requirements, and the ability to produce consistent, repeatable results are critical to the individual manufacturing application. Use of beamsplitters introduces technical challenges in maintaining the consistency and repeatability of laser milling. Thus, the need remains for a method of design and apparatus for control of multiple beam intensity distributions that solves several problems that continue to exist in the field of material ablation with pulsed light sources.
One problem that continues to exist in the field of material ablation with pulsed light sources relates to creating multiple holes or shapes in a material that meet customer requirements for hole uniformity and repeatability. Current methods for parallel laser drilling of multiple holes in a workpiece include the use of a conventional diffractive optical element (DOE) to split a single beam into multiple sub-beams. However, because typical DOEs do not produce sub-beams of equal uniformity, the laser drilling system in turn does not provide the consistent, repeatable hole geometry that is required in the marketplace. Consistency and repeatability of multiple holes, and meeting customer specifications for those holes, is critical in micromachining applications. What is needed is a way to create multiple holes or shapes in a material that meet customer requirements for hole uniformity and repeatability.
Another problem that continues to exist in the field of material ablation with pulsed light sources relates to providing beam intensity equalization in a laser drilling system. DOEs are typically designed to divide a single laser beam into multiple beams of equal intensity. However, due to design limitations and manufacturing flaws, many DOEs do not provide equal or sufficiently uniform beam intensities across all sub-beams. If a DOE is not designed to compensate for its design weaknesses, other elements in a laser drilling system must be added or changed to compensate for this deficiency. What is needed is a way to provide beam intensity equalization in a laser drilling system.
Laser milling has historicall
Cheng Chen-Hsiung
Liu Xinbing
Harness Dickey & Pierce PLC
Heinrich Samuel M.
LandOfFree
System and method of laser drilling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method of laser drilling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method of laser drilling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3269790