Patent Application
20100269853
Various embodiments described herein relate generally to approaches for extracting debris and other material using an exhaust system, and in some instances relate specifically to an exhaust system that extracts debris for a laser-scribing system, as well as methods and apparatus for using such an exhaust system. Many of these methods and apparatus can be particularly effective when applied to extract debris in a laser-scribing system that is used to form thin-film multi-junction solar cells.
Current methods for forming thin-film solar cells involve depositing or otherwise forming a plurality of layers on a substrate, such as a glass, metal or polymer substrate suitable to form one or more p-n junctions. An example of a solar cell has an oxide layer (e.g., a transparent conductive oxide (TCO)) deposited on a substrate, followed by an amorphous silicon layer and a metal back layer. Examples of materials that can be used to form solar cells, along with methods and apparatus for forming the cells, are described, for example, in co-pending U.S. patent application Ser. No. 11/671,988, filed Feb. 6, 2007, entitled “MULTI-JUNCTION SOLAR CELLS AND METHODS AND APPARATUSES FOR FORMING THE SAME,” which is hereby incorporated herein by reference. When a solar panel is being formed from a large substrate, a series of laser-scribed lines is typically used within each layer to delineate individual cells.
The laser-scribed lines are formed by ablating material from a workpiece, which consists of a substrate and deposited layers. This is achieved by concentrating a large amount of energy into a very short duration laser pulse and choosing the optimal laser wavelength to couple with the material. When the correct conditions for ablation are achieved, the material is removed in an explosive plume that contains debris. Debris from the laser-scribing process is normally removed using an extraction unit. In previous approaches, the debris is captured in a close fitting hood and then conveyed, entrained in air, by ductwork to a debris-extraction unit where the debris is removed from the airflow. The airflow used to remove the debris imparts a large lifting force on the workpiece, which in turn affects the distance between the workpiece and the laser. If the airflow is reduced to lower the lifting force on the workpiece, then the air velocity might become too low to effectively remove all debris. Therefore, there is a need for an improved exhaust system that will effectively and efficiently remove debris without imparting a large lifting force.
The previous approaches also exhibited other deficiencies. For example, the close-fitting hood formed an enclosure over a portion of the workpiece that was being scribed. Airflow from the exhaust system made it difficult to control the stability of the temperature inside the enclosure, which is critical to the laser-scribing process due to sensitivity of the laser scanners to temperature. Furthermore, an exhaust system with a large exhaust load and air conditioning requirement increased operational costs.
Accordingly, it is desirable to develop systems and methods that overcome at least some of these, as well as potentially other, deficiencies in existing debris-extraction systems and methods for laser scribing and solar panel manufacturing devices. Further, it can also be seen that this need for better debris extraction may also exist for direct patterning of large masks for flat panel displays and direct patterning for other large display applications, such as black matrix ablation.
The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later.
Systems and methods for extracting debris from a workpiece during laser scribing are provided. Various embodiments can provide for efficient and effective debris removal from an active area of a workpiece by introducing a flow of supply air to an active area of the workpiece. The flow of supply air can help reduce the magnitude of the lifting force imparted on the workpiece. Additionally, the flow of supply air can help to stabilize the temperature within the active area, which may help to stabilize the laser-scribing process. Such systems and methods can be configured for reduced exhaust system load and/or reduced air conditioning and/or heating requirements, thereby lowering costs, such as initial cost and operational cost.
In an embodiment, a debris-extracting exhaust system is provided. The system includes an extraction nozzle that includes at least one debris-extraction orifice. Each debris-extraction orifice is configured for placement adjacent to an active area of a workpiece. The system includes a source of exhaust operable to extract a flow of exhaust and debris from the active area through each debris-extraction orifice. The extraction nozzle includes, for each debris-extraction orifice, a first duct coupled with the debris-extraction orifice and a second duct coupled with the debris-extraction orifice. The second duct is configured to deliver a flow of supply air towards the active area and the first duct is configured to remove a flow of exhaust air and debris from the active area.
A debris-extracting exhaust system can involve a variety of options. For example, the second duct can enclose at least a portion of the first duct. The second duct can discharge the supply air at the perimeter of the debris-extraction orifice. A system can include a filtering device for removing the debris from the flow of exhaust air, whereby the filtered exhaust air is able to be re-circulated into the flow of supply air. The filtering device can include a particle filter and/or a chemical filter. Each debris-extraction orifice can be configured to extract debris from a single laser-scribing area, wherein the laser-scribing area is an area of the workpiece that can be processed by a laser scanner. A system can include a translation mechanism for moving the extraction nozzle so that each debris-extraction orifice is moved in coordination with movement of the active area. The system can be configured to ensure that airflow velocities within the first duct are sufficiently high to capture and convey substantially all debris from the workpiece, and to ensure that no vortex is formed within the first duct that will trap the debris and prevent the debris from being conveyed along the first duct. The system can be configured such that a separation distance between the debris-extraction orifice and the workpiece is adjustable. The extraction nozzle can include at least one end piece that can be removed for maintenance, cleaning, and/or geometric modification. Each end piece can define the debris-extraction orifice. The system can be configured such that a pressure differential between opposing sides of the active area is less than a desired value.
In another embodiment, a method of using airflow to remove debris from a workpiece is provided. The method includes providing a flow of supply air, discharging the flow of supply air toward an active area of a workpiece, and extracting a flow of exhaust air and debris from the active area through a debris-extraction orifice.
A method of using airflow to remove debris from a workpiece can involve a variety of options. For example, the direction and rate of flow of the supply air can be sufficient to maintain a minimum separation between the workpiece and the debris-extraction orifice. A method can include filtering the flow of exhaust air to substantially remove the debris and re-circulating air from the filtered flow of exhaust air into the flow of supply air. The flow of exhaust air can be filtered by processing through a particle filter and/or a chemical filter. The discharge of the flow of supply air and the extraction of the flow of exhaust air can be substantially limited to one or more areas of the workpiece that are being laser scribed. The flow of supply air can be provide through a first duct to deliver the flow of supply air along an extraction nozzle toward the active area. The flow of exhaust air and debris can be extracted through a second duct to deliver the exhaust air and debris along the extraction nozzle away from the active area.
In another embodiment, a debris-extracting exhaust system is provided. The system includes a plurality of extraction nozzles with each nozzle including a debris-extraction orifice configured for placement adjacent to an associated active area of a workpiece. The system further includes a source of supply air operable to direct a flow of supply air through a first duct of each extraction nozzle toward the associated active area, and a source of exhaust operable to extract a flow of exhaust air and debris from the associated active area through each second duct.
A debris-extracting exhaust system can involve a variety of options. For example, the direction and rate of flow of the supply air can be sufficient to maintain a minimum separation between the workpiece and each extraction nozzle. A system can be configured such that a pressure differential between opposing sides of each active area is less than a desired value. A system can include a filtering device for removing debris from the flows of exhaust air, whereby the filtered exhaust air is able to be re-circulated into the flows of supply air. A system can include a translation mechanism for moving the extraction nozzles so that each debris-extraction orifice is moved in coordination with movement of its associated active area.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings. Other aspects, objects and advantages of the various embodiments will be apparent from the drawings and detailed description that follows.
Various embodiments in accordance with the present invention will be described with reference to the drawings, in which:
In the following description, various embodiments of the present disclosure will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.
Systems and methods in accordance with various embodiments of the present disclosure can overcome one or more of the aforementioned and other deficiencies in existing debris-extracting exhaust system approaches. Various embodiments can provide for greatly reduced lifting force on the workpiece, which may help maintain a desired workpiece separation distance, as well as to provide better temperature control and lower operating cost. Devices in accordance with various embodiments can provide efficient and effective exhaust system approaches for removing debris through the use of multiple extraction nozzles, which can be shaped to only cover each individual laser-scribing areas and which can be configured to move together with the laser-scribing areas. These systems and methods can be particularly effective when applied to debris-extracting exhaust systems for laser scribing and solar panel manufacturing devices. They can also be effective in other applications, such as when applied to debris-extracting exhaust systems for direct patterning of large masks for flat panel displays and direct patterning for other large display applications such as black matrix ablation.
In many embodiments, efficient and effective debris extraction from an active area of a workpiece may be realized with an exhaust system having a supply air feature that delivers a flow of supply air to the active area. A flow of exhaust air containing debris and at least a portion of the supply air is then extracted from the active area. The flow of supply air helps to avoid subjecting the active area to reduced pressure that may exist in some prior exhaust systems. In some prior exhaust systems, the flow of exhaust air is drawn from outside of an exhaust nozzle through a gap between the exhaust nozzle and the workpiece. The flow of air through the gap creates a pressure drop, which typically creates a lifting force on the workpiece due to the lack of a balancing pressure drop on the opposing side of the active area. A debris-extraction exhaust system having a flow of supply air can be configured such that a pressure differential between opposing sides of the active area is less than a desired value (e.g., less than 1.0 psi as a non-limiting example). By avoiding this reduction in pressure, the introduction of the flow of supply air reduces the lifting force imparted on the workpiece. The reduced lifting force helps to ensure that the exhaust system has a reduced impact on the separation distance between the workpiece and adjacent components (e.g., exhaust system extraction nozzle(s), laser focusing optics, lasers focused on the workpiece, etc.), and in fact can help control these separation distances through pressure control. The temperature of the supply air can be controlled so as to increase the stability of the temperature of the active area (e.g., the temperature inside an exhaust system extraction nozzle and/or close fitting hood positioned adjacent to the active area). This increased stability of temperature may help to stabilize the laser-scribing process due to sensitivity of laser scanners to temperature. Further, operation of an exhaust system with such a reduced exhaust load and air conditioning requirement may reduce facility costs.
In many embodiments, the flow of exhaust air and debris can be filtered to remove the debris. The filtering can be accomplished using known filters (e.g., particle filters, chemical filters, etc.). Some or all of the filtered exhaust air can be re-circulated into the flow of supply air. Re-circulation of filtered exhaust air may help to stabilize the temperature of the flow of supply air, thereby helping to stabilize the temperature in the active area, which may help to stabilize the laser-scribing process as discussed above. Re-circulation of filtered exhaust air may also reduce the amount of heat that must be added or subtracted from the flow of supply air to achieve a desired temperature for the flow of supply air, which may help to reduce air conditioning and/or heating costs as the case may be depending upon the surrounding ambient temperature.
A laser-scribing system may have more than one laser scribing the workpiece simultaneously to increase throughput. This results in a plurality of laser-scribing areas, which correspond to the scan fields of the laser scanners. (Note: The scan field corresponds to the area that can be scribed by the laser.) In many embodiments, instead of having a single large close fitting hood cover over all the individual laser-scribing areas, a plurality of separate extraction nozzles can be used to cover over each laser-scribing area. This results in much more efficient debris extraction by limiting exhaust airflow only to areas where there is debris to be extracted. This in turn also helps to reduce the lifting force imparted on the workpiece, as well as the load on the exhaust blower. The operation of an exhaust system with a reduced exhaust blower load can be done with a smaller blower that uses less power, thereby further reducing costs.
The multiple scribing lasers described previously can be mounted on a support that is able to translate on a lateral rail as driven by a controller and servo motor. Accordingly, the laser-scribing areas described previously would be able to move laterally as the scribing lasers themselves and their support are also moved laterally on the rail. In many embodiments, the plurality of separate extraction nozzles described earlier can be moved in coordination with the motion of the laser(s) below the glass substrate. This allows separate extraction nozzles to cover individual laser-scribing areas, which creates a more efficient debris extraction by limiting exhaust airflow only to areas where there is debris to be extracted. This in turn also helps to reduce the lifting force imparted on the workpiece, as well as the load on the exhaust blower.
In many embodiments, an exhaust system can be configured so as to produce sufficient airflow velocities adjacent the active area to extract substantially all particles (of the debris) from the active area and also prevent low velocity areas where particles (of the debris) can fall out of the airflow. For example, flow rates, cross-sectional areas, and internal contours can be selected and the resulting airflows can be predicted using known analytical methods and/or can be measured. A system can be configured such that the resulting airflows are sufficient to capture and convey particles (of the debris) in vertical and horizontal runs. A system can be configured such that low velocity areas are not formed where particles (of the debris) can fall out of the airflow and onto the workpiece, hood, or ducting. A system can be configured such that vortices are also not formed that will trap particles (of the debris) and prevent them from being conveyed to the filtration units.
An extraction nozzle in embodiments can be easily adjusted to optimum working height over the workpiece. In some embodiments, this can be accomplished through a combination of mechanical position control and pressure control of the flow of supply air and/or of the flow of exhaust air and debris. An extraction nozzle can be configured with removable/replaceable parts, which can provide for potential future geometric changes to improve exhaust airflow characteristics, as well as for easy maintenance and cleaning. An exhaust system can be grounded to prevent static build-up and for safety.
The extraction nozzle 116 comprises of two separate ducts: an inner duct 120 that removes a flow of exhaust air and debris from the workpiece 104 and an outer duct 122 that discharges a flow of supply air to the workpiece 104. The outer duct 122 can at least partially surround the inner duct 120, such as by a uniform spacing. Exhaust 124 removes the “exhaust air” from the inner “exhaust air” duct 120, while air supply 126 supplies the “supply air” into the outer “supply air” duct 122.
The extraction nozzle 116 is separated from the workpiece 104 by an extraction gap 128 (which, as an example, may be equal to 3 mm). Air bearings 130 forming, as an example, a 40˜100 μm air gap 132 can be used to support the workpiece 104 over the stage 102, although rollers or other bearing- or translation-type objects can also be used to receive and translate the workpiece 104 as known in the art.
The example exhaust system of
Further, the flow of exhaust air and debris that is pulled back into the exhaust system can be cleaned and at least partially directed back toward the workpiece by re-circulation into the flow of supply air. This return air feature may provide for increased stability in temperature of the active area of the workpiece 104, as pulling in air from the exterior through the peripheral gap may impact the temperature of the active area depending upon the temperature of the external air. The return air feature may stabilize the laser-scribing process due to sensitivity of the laser scanners to temperature. Without such a return air feature, it may be necessary to adjust the temperature of the external air using air conditioning or heating depending upon the temperature of the external air. Accordingly, the operation of an exhaust system with reduced air conditioning and/or heating requirements may help to decrease costs. The exhaust air can be re-circulated back to the supply air input after substantially removing the debris (e.g., by filtering through a particle filter, by filtering through a chemical filter, or by using know debris removal processes). Note that
As discussed, a laser-scribing system can have more than one laser scribing the workpiece simultaneously to increase throughput. This results in a plurality of laser-scribing areas, which correspond to the scan fields of the laser scanners. Each scan field can correspond to an area or region that is capable of being scribed by output from a respective laser. Therefore, instead of having a single large close fitting hood cover over all the individual laser-scribing areas, a plurality of separate extraction nozzles can be used to cover over each laser-scribing area. This may result in much more efficient debris extraction by limiting exhaust airflow to areas where there is debris to be extracted. This in turn may help to reduce the lifting force imparted on the workpiece, as well as the load on the exhaust blower. As an example,
The extraction nozzle 116 illustrated in
Such computer simulations can be used to configure the exhaust system and extraction nozzle to produce sufficient airflow velocities to extract substantially all particles (of the debris) from an active area of a workpiece and also prevent low velocity areas where particles (of the debris) can fall out of the airflow. Airflow velocities of sufficient magnitude can be produced to capture and convey particles (of the debris) in vertical and horizontal runs. Low velocity areas can be avoided where particles (of the debris) may fall out of the airflow and onto the workpiece, hood, or ducting. Vortices can be avoided that may trap particles (of the debris) and prevent them from being conveyed to the filtration units.
The computer simulation further illustrates the operation of an extraction nozzle in accordance with embodiments. The flow of supply air 202 travels down an outer duct where it is discharged to the active area of the workpiece at the perimeter of the debris-extraction orifice. A flow of gap air 204 is drawn through the perimeter gap. The flow of supply air 202 and the flow of gap air 204 combine in the region of the debris-extraction orifice of the extraction nozzle, thereby supplying the flow of air that becomes the flow of exhaust air 206. The combined action of the air flows serves to remove debris from the active area of the workpiece.
The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims. Further, embodiments may be implemented individually or in any combination as needed to realize benefits of the present invention.
This application claims the benefit of U.S. Provisional Patent Application No. 61/050,944, filed May 6, 2008, entitled “RECIRCULATING EXHAUST FOR DEBRIS EXTRACTION,” which is hereby incorporated herein by reference.
