US20100252605A1

US20100252605A1 - Web support assembly

Info

Publication number: US20100252605A1
Application number: US12/418,025
Authority: US
Inventors: Mark Lycette; Joachim Doehler; James Blyth
Original assignee: United Solar Ovonic LLC
Current assignee: United Solar Ovonic LLC
Priority date: 2009-04-03
Filing date: 2009-04-03
Publication date: 2010-10-07

Abstract

A web support assembly for a moving web of substrate material includes a base having a primary support arm pivotally mounted thereto so as to be displaceable from a first position to a second position. The web support assembly includes a first biasing member in mechanical communication with the primary support arm. The first biasing member operates to impart a first biasing force to the primary support arm so as to move it from its first position to its second position. The system includes a dancer arm which is pivotally mounted to the primary support arm so as to be displaceable from a first position to a second position relative primary support arm. The web support assembly further includes a second biasing member in mechanical communication with the dancer arm. The second biasing member operates to impart a second biasing force to the dancer arm so as to move it from its first position to its second position. A roller is rotatably supported on the dancer arm. The roller is configured to engage a portion of the web. The web support assembly operates to maintain continuous contact between the roller and the moving web of substrate material as it passes through a multi-station processing system.

Description

FIELD OF THE INVENTION

This invention relates, generally, to assemblies for supporting and guiding a moving web of substrate material. More specifically the invention relates to assemblies for supporting an end portion of a vertically disposed, elongated web of substrate material as it moves through a multi-station processing system. In particular the invention relates to an assembly for supporting and guiding a vertically disposed web of substrate material in a system for the continuous production of photovoltaic devices.

BACKGROUND OF THE INVENTION

Systems and methods have been developed for the high volume fabrication of photovoltaic devices. In such processes, one or more webs of substrate material, typically stainless steel, are continuously fed from a payout chamber through a plurality of deposition stations in which layers of semiconductor material are sequentially deposited onto the webs. The coated webs are then wound onto rolls in a take-up chamber and removed for subsequent processing into photovoltaic modules. In particular systems of this type, the web or webs of substrate material are maintained in a vertical orientation as they pass through the deposition apparatus. Some systems of this type are shown, for example, in U.S. Pat. No. 4,423,701 and in published U.S. patent application 2004/0040506, which are incorporated herein by reference.
Web transport and guidance are critical parameters in deposition systems of this type. In order to assure deposition of high quality semiconductor layers, precise tolerances must be maintained between the moving substrate web and active components of the deposition system. Likewise, the moving web must travel along a precise path through the various chambers so as to avoid binding, twisting or other deformations which could compromise the integrity of the substrate web or the deposition system. All of these problems are complicated by the fact that deposition systems of this type frequently have about 300 foot or more lengths of substrate web actively moving therethrough at any time, and a typical substrate material has a weight of approximately ¼ pound per linear foot. The relatively heavy, relatively long substrate can cause problems of sagging and twisting since gravity tends to urge the substrate into a catenary configuration, and these problems can be enhanced by web geometry variation and differential thermal expansion of the web in the apparatus.
In apparatus of this type, transport systems for the substrate web must also be designed so as to avoid making contact with semiconductor material deposited on the active face of the substrate web, since such contact could degrade the operational performance of the semiconductor device. And finally, substrate transport systems must also be designed so as to avoid bending, burring or other deformation of the substrate web, since such damage will prevent the coated substrate material from being wound into a uniform roll. This factor is critical since any such non-uniformity in the roll can damage the sensitive semiconductor layers during subsequent processing. In one prior art approach as is disclosed in published U.S. patent application 2006/0278163 a substrate support system incorporates a magnetic guidance assembly and a number of support rollers to transport vertically oriented webs through a deposition system.
The rollers of the system in the '163 patent application guide and direct edges of the moving web. However, in the operation of systems of this type it has been found that problems can arise because of irregularities in the web material itself as a result of geometric variations in the manufacture of the web and/or deformations resultant from differential thermal expansion. As a result of such variations, the amount of force exerted by the moving substrate web on any one roller may vary as the web moves therethrough. Excessive force between the roller and the web can deform the edge of the web creating a burr, buckle or bend. Decreased force between the roller and the web can also be a problem, particularly if the web moves away from the roller since, under the high vacuum, relatively high temperature conditions encountered in the deposition chamber, cold welding of the substrate and roller can occur when contact is reestablished causing damage to the web and/or the roller. Therefore, there is a need for a web support system which can operate to reliably and precisely move relatively heavy, long webs of substrate material through a multistage high vacuum deposition system of the type used for the manufacture of photovoltaic devices and other semiconductor devices. Any such system should be relatively simple and reliable in its operation and should be compatible with high vacuum, ultra clean conditions and should not introduce contamination into the system.
As will be explained in detail hereinbelow, the present invention provides a web transport system which can be incorporated into multi-station processing systems, for example, high volume systems for the continuous preparation of photovoltaic and other semiconductor devices. These and other aspects and advantages of the present invention will be apparent from the drawings, discussion and description which follow.

SUMMARY OF THE INVENTION

The present invention comprises a web support assembly for a moving and guiding web of material. In a specific instance, the web support assembly includes a base, a primary support arm which is pivotally mounted to the base so as to be displaceable from a first position to a second position relative to the base, and a first biasing member which is in mechanical communication with the primary support arm. The first biasing member is operable to impart a first biasing force to the primary support arm so as to move it from its first position to its second position. The web support assembly further includes a dancer arm which is pivotally mounted on the primary support arm so as to be displaceable from a first position to a second position relative to the primary support arm. A second biasing member is in mechanical communication with the dancer arm. The second biasing member is operable to impart a second biasing force to the dancer arm so as to move it from its first position to its second position. The web support assembly furtier includes a web support roller which is rotatably supported by the dancer arm. The roller is configured to engage a portion of the web. In specific instances, the first biasing force is greater than the second biasing force. In particular instances, the biasing members may be springs, elastomeric bodies, pneumatic cylinders, magnetic devices, hydraulic cylinders, and various combinations of the foregoing.
In a specific instance, the first biasing member is a spring which extends between a primary support arm and the base. In some instances, the second biasing member may be a spring which extends between the dancer arm and the primary support arm.
In specific instances, the web support roller includes a groove which is configured to engage a web, and this groove may, in particular instances, be an asymmetric groove. In some instances, the asymmetric groove may be configured so that the two faces of the groove form a 90 degree angle. In specific instances, the groove is configured so that an end surface of the substrate does not contact the base of the groove.
Further disclosed is an apparatus for the continuous deposition of a layer of semiconductor material onto an elongated web of substrate material which is advanced therethrough, wherein the apparatus includes the web support assembly of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a web support assembly of the present invention;

FIG. 2 is a perspective view of the web support assembly of FIG. 1 showing a web of substrate material engaged therewith;

FIG. 3 is perspective view of a primary support arm and a dancer arm of the web support assembly of FIG. 1;

FIG. 4 is an illustration of the web support assembly of FIG. 1 in a down position wherein a high substrate load is imposed thereupon;

FIG. 5 is a depiction of the web support assembly of FIG. 1 in an up position wherein a low level of contact force is imposed on the substrate; and

FIG. 6 is a cross-sectional view of a portion of a roller of the present invention as engaged with a web of substrate material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a web transport system which includes a number of web support assemblies which may be utilized to support and guide a substrate material through a processing system. In that regard, the invention will have utility in a large number of systems wherein transportation of a web of material is an aspect of the processing system. The present invention will be described with regard to a specific utility wherein it is employed to guide and support a substrate web in a system for the high volume deposition of photovoltaic semiconductor material in a continuous roll-to-roll process.
The web support assemblies of the present invention are configured so as to maintain a portion of the web support in continuous contact with an edge of the substrate despite fluctuations in substrate width and/or position. Furthermore, the web support assembly is configured so that excessive force between the edge of the substrate web and the contacted support is minimized. In exemplary embodiments, the web support assembly includes a multi-biasing arrangement configured to bias the substrate web between a first position and a second position. In an exemplary embodiment, the multi-biasing arrangement includes a biasing force transition zone with a discontinuous contact force at a web/support contact location. In an exemplary embodiment, a portion of the web in contact with the web support has a deflection that is substantially zero within the biasing force transition zone. In exemplary embodiments, the web support assembly biases the web with a greater biasing force along a first direction compared to a biasing force exerted upon the web along a second direction.
The system of the present invention may be implemented in a number of embodiments. One specific embodiment as particularly adapted for use in an apparatus for the fabrication of photovoltaic devices will be shown herein. In some embodiments, a first plurality of web support assemblies will be utilized to support/guide a first edge of a substrate web, while one or more web support assemblies are used to support/guide a second edge of the substrate web. In certain embodiments, a portion of the plurality of web support assemblies will be configured different from the other web support assemblies along the first and/or second edges of the web, for example, in terms of structural configuration, load/temperature capability, materials, etc. However, it is to be understood that other embodiments of the invention may be implemented, and likewise, the systems and apparatus of the present invention may be incorporated into systems utilized for the manufacture of a variety of materials. It is to be further understood that the Figures of this application are not drawn to scale, rather the Figures are drawn to illustrate most clearly the principles of this disclosure discussed herein.
Referring now to FIGS. 1 and 2, there is shown a web support assembly 10, configured in accord with an embodiment of the present invention. The web support assembly 10 includes a base portion 12 which functions to support the remainder of the assembly and further functions to allow the assembly to be mounted to other structure. The base 12, as well as other portions of the web support assembly, can be fabricated from materials that withstand loads applied thereto and that do not degrade processes of the system. For example, it would not be desirable where a material of the web support assembly releases gases or other contaminate that degrades the integrity of a semiconductor deposition process. In certain embodiments, the assembly materials include aluminum, mild or high-strength steel, stainless steel, a high strength plastic, and combinations thereof. In the present embodiment unless otherwise noted herein, the majority of the assembly components are made from aluminum. A primary support arm 14 is pivotally mounted to the base 12 by a pivot joint 16 which allows the primary support arm 14 to be movable from a first position to a second position, relative to the base.
The web support assembly also includes a biasing member, in this instance a coil spring 18 which is mounted between the base 12 and the primary support arm 14. The coil spring 18 operates to exert a biasing force which tends to move the primary support arm from a first position to a second position. In many embodiments, the spring 18 will be preloaded a predetermined amount, for example, to urge the primary support arm upward as shown in FIG. 1 (e.g. second position), to suit a configuration of web (e.g. geometry and weight) and web movement parameters in the processing system. While the biasing in the FIG. 1 embodiment is accomplished by the coil spring 18, other biasing members such as elastomeric bodies of material such as synthetic or natural rubber may be used to provide the biasing force. Yet other biasing mechanisms known in the art such as gas filled pneumatic cylinders, hydraulic cylinders, counterweights, magnetic devices (including electromagnetic devices) and the like may also be used as biasing members. Also, while the spring 18 is shown as being in a particular location between the base 12 and support arm 14, it will be appreciated that it could be otherwise disposed. For example, the biasing may be accomplished by a coil spring associated with the pivot 16. Alternatively, the biasing member need not be in any mechanical communication with the base. For example, biasing may be accomplished by a spring or elastomeric body extending between the primary support arm 14 and some other portion of the apparatus in which the system is disposed.
The web support assembly 10 of FIGS. 1-3 further includes a dancer arm 20 which is pivotally supported on the primary support arm 14, in this instance Through a pivot joint 22. A second coil spring 24 is disposed between the dancer arm 20 and primary support arm 14 and it operates to bias the dancer arm 20 between a first and second position relative to the primary support arm 14. As discussed with regard to the first spring 18, the second spring 24 may be otherwise disposed; or, it may comprise another type of biasing member such as an elastomeric body, pneumatic cylinder, hydraulic cylinder, counterweights, magnetic device or the like. Rotatably affixed to the dancer arm 20 (at hole 28 shown in FIG. 3) is a support roller 26, which operates to engage an edge of a web of substrate material, and as such it may be grooved or otherwise configured to aid in its retention of the web. In this embodiment, the support roller is primarily made of substantially non-magnetic, 304 stainless steel. In an alternative embodiment, the support roller can include a ceramic material that contacts the web.
Referring now to FIG. 2, there is shown a perspective view of the web support assembly 10 of FIG. 1 with a portion of a web of substrate material 30 engaged therewith. It is to be understood that in a typical application the substrate material 30 comprises an elongated web of material; however, for purposes of simplification, only a portion of the web is shown in FIG. 2. Additionally, the embodiment of web support assembly shown in FIG. 2 is configured so two webs can be independently guided/supported, wherein each roller supports/guides a web moving over the roller independent from the other web-roller interaction, For clarity purposes only one web is shown in phantom outline in FIG. 2, It is to be understood that even though only one side (one web support) of FIG. 2 has reference numerals and the same side is shown other Figures, the principles discussed herein with respect to the parts denoted by reference numerals apply to the other web support without reference numerals in FIG. 2.
In the FIG. 2 illustration, the support roller 26 has engaged the edge of the vertically disposed substrate 30, and as will be seen, a groove 27 in the roller facilitates retention of the substrate 30. Referring to FIG. 4, the weight of the substrate 30 bearing onto the roller 26 has compressed the second coil spring (24 shown in FIG. 1) between the dancer arm 20 and primary support arm 14. The biasing force of the second spring has, in this embodiment, been selected so as to be less than the biasing force of the first spring 18 and sufficient to overcome the weight of the dancer arm and roller. In the FIG. 2 configuration the first spring 18 is supporting the primary arm 14, the dancer arm 20 and the roller 26 against the downwardly exerted force of the substrate 30. If that force increases because of distortions of the substrate web or the like, the spring 18 will absorb further downward force preventing damage to the web while maintaining good contact with the web. Distortions of the substrate web can be caused, in non-limiting examples, from web geometry variations, thermal and dynamic loads, etc. For example, if a portion of the bottom surface/edge of the substrate web being supported by the roller is disposed below a theoretical pass line of the web, the web will tend to exert a contact force upon the roller to move the roller toward a position shown in FIG. 4. Here the theoretical pass line is a line of travel of the bottom surface/edge of the web if it was perfectly straight, or the web bottom surface pass line has no distortions from that line due to part/web geometry variation, thermal and dynamic loads, movement parameters, etc. In this embodiment, the first spring is configured so a threshold predetermined contact force between the roller and the web is not exceeded. The threshold contact force can be based on deformation, web/roller deflection, material yield, etc. In this embodiment, the threshold contact force is based on a predetermined force that will not deform the web, e.g. dent, crease etc., beyond a predetermined amount when the web is disposed below the pass line.
In that regard, FIG. 4 shows a side elevation view of the assembly 10 in a downwardly biased position. In the event that the web downward force decreases, the spring 18 will bias the primary support arm 14, the associated dancer arm 20 and roller 26 back toward a neutral position. Should the web downward force still decrease, as would be the case if the web were moving so as to lift from the roller, e.g. when the bottom surface of the web moves above the theoretical pass line, the spring 18 will drive the primary support arm 14 to its full extent of travel as is shown in FIGS. 2, 3, 5; and at that point, the second spring 24 will operate to lift the dancer arm 20 so as to further raise the support roller 26 and thereby maintain contact with the edge of the web. As noted above, the biasing force of the second spring 24 is generally less than that of the first spring 18. Therefore, the pressure exerted by the roller onto the web will be less than it would be in a full downward contact position; but such pressure will be sufficient to maintain the two in contact and prevent the web from leaving the roller. The biasing forces of the springs can be selected based upon specifics of a processing system and a substrate web as will be discussed hereinbelow. In this embodiment, the first and second springs are configured to provide a discontinuous transition of contact force between the roller and web when the roller is in a force transition zone between the roller positions of FIGS. 4 and 5. Within that transition zone there is a position where the vertical displacement of the roller is substantially zero and the force between the web and roller either increases or decreases depending on the whether the web is moving toward a direction below or above the pass line. In the embodiment described hereinabove, the web support can be considered to bias the substrate web between a position below the theoretical pass line, similar to that shown in FIG. 4, and another position above the pass line, similar to that shown in FIG. 5.
The rollers used to contact and support/guide the web may be variously configured. In this embodiment, the roller includes a groove or some other feature for maintaining the substrate and roller in engagement. Referring now to FIG. 6, there is shown a portion of a roller 26 of the present invention having a web of substrate material 30 engaged with a groove 27 therein as shown in FIG. 2. In the FIG. 6 embodiment the groove is an asymmetric groove. That is to say, the two faces of the groove have different angles of contact with the substrate 30. The groove has a first face 32 which contacts an edge of a first face or surface of the substrate 30 at a first angle A, which in some embodiments is in the range of 5 degrees to 45 degrees. The groove includes a second face 34 which contacts an edge of a second face or surface of the substrate 30 at a second angle B which in some embodiments is in the range of 5 degrees to 30 degrees. In particular instances, angle B is greater than the angle A. Furthermore, in this embodiment, angle A and angle B are complementary angles; that is to say, they add up to 90 degrees. In specific instances, the system is configured so that the deposition of the semiconductor material takes place on the face of the substrate 30, which defines angle A. Other angular relationships and orientations may be implemented. It will also be seen that in the FIG. 6 illustration the face or the end surface of the substrate web 30 does not contact the base of the groove. Contact between the roller 26 and the web 30 is established by a pinch between the faces 32, 34 of the roller and the edges or corners of the web. It has been found that this type of contact provides desirable web support/guidance and further prevents damage to the face or end surface of the substrate web.
In systems for the deposition of semiconductor material onto a moving substrate web wherein the semiconductor deposition takes place on the face of the web closest to roller face 32, very good results are found utilizing the geometric relationships of FIG. 6. In this regard, a roller configured as per FIG. 6 is very effective in maintaining the substrate 30 in a precise alignment with a deposition station while avoiding damage to the substrate.
In view of the foregoing, various support assemblies may be readily configured by those of skill in the art. The precise dimensions and characteristics of the assembly will depend upon particular applications. As discussed above, a typical high volume continuous process apparatus for the deposition of semiconductor material may employ stainless steel substrate material having a weight of approximately ¼ pound per linear foot. In one system of this type, the substrate material is supplied in coils of approximately 8000 feet in length, and at any one given time approximately 279 feet of the substrate web is actively moving through the deposition system. And as is further noted, such systems may include up to 6 webs moving therethrough in a substantially parallel relationship. In this configuration, each web has 60 supports associated therewith. Therefore, each roller will be supporting approximately 1.16 pounds on the average. In a system of this type, the primary spring (18 hereinabove) will typically be preloaded to a level of approximately 2.5 to 3.5 pounds and the dancer spring (24 hereinabove) will be selected so that a load of 0.75 to 1 pound will compress it to its fully down position, as shown in FIG. 4. In instances where differently configured systems and/or substrate webs are employed, the biasing force of the springs or other biasing members may be adjusted accordingly.
The web support assembly of the present invention has been described with regard to its use to support and guide the bottom edge of a vertically disposed substrate. However, assemblies of this type may also be disposed to engage a top edge of a vertically disposed substrate. In such instances, the biasing forces may be adjusted accordingly. Also, the support assembly has been described with regard to its use in conjunction with steel substrates. It is to be understood that such assemblies may be used to support and guide other types of substrate webs, including polymeric substrates, composite substrates, fibrous substrates and the like.
In view of the teaching presented herein, other modifications, variations and embodiments of this invention will be apparent to those of skill in the art. All of such embodiments are within the scope of this invention. The foregoing drawings, discussion and description are illustrative of specific embodiments of the invention, but are not meant to be limitations upon the practice thereof. It is the following claims, including all equivalents, which define the scope of the invention.

Claims

1. A web support assembly for a moving web of material, said web support assembly comprising:

a base;

a primary support arm which is pivotally mounted on the base so as to be displaceable from a first position to a second position relative thereto;

a first biasing member in mechanical communication with said primary support arm, said first biasing member being operable to impart a first biasing force to said primary support arm so as to move said primary support arm from its first position to its second position;

a dancer arm which is pivotally mounted on said primary support arm so as to be displaceable from a first position to a second position relative to said primary support arm;

a second biasing member in mechanical communication with said dancer arm, said second biasing member being operable to impart a second biasing force to said dancer arm so as to move said dancer arm from its first position to its second position; and

a web support roller rotatably supported by said dancer arm, said roller being configured to engage a portion of said web.

2. The web support assembly of claim 1, wherein said first biasing force is greater than said second biasing force.

3. The support of claim 1, wherein said first biasing member and said second biasing member are selected from the group consisting of: springs, elastomers, pneumatic cylinders, hydraulic cylinders, magnetic devices, and combinations thereof.

4. The support of claim 1, wherein said first biasing member is a spring which extends between said primary support arm and said base.

5. The support of claim 1, wherein said second biasing member is a spring which extends between said dancer arm and said primary support arm.

6. The support of claim 1, wherein said web support roller includes a groove which is configured to engage an edge of the web.

7. The support of claim 6, wherein said groove is an asymmetric groove.

8. The support of claim 6, wherein said groove includes a first face and a second face, and wherein said first face and said second face form a 90 degree angle.

9. The support of claim 6, wherein said groove is configured so that said groove includes a first face and a second face, and wherein said faces establish a pinch contact with said substrate so that an end surface of said substrate does not contact the bottom of said groove.

10. The support of claim 6, wherein said roller is configured so that when the substrate material is disposed within the groove, a first face of said groove forms a first angle A, with a first face of said web, and a second face of said groove forms a second angle B with a second face of said web, and wherein angle A and angle B are different.

11. The web support assembly of claim 10, wherein angle A and angle B are complementary.

12. An apparatus for the continuous deposition of a semiconductor material onto an elongated web of substrate material which is advanced therethrough, said apparatus including the web support assembly of claim 1.

13. The web support assembly of claim 1, further comprising a second web support assembly configured to support a second moving web, said first and second webs in a spaced, substantially parallel relationship.

14. The web support assembly of claim 13, wherein the web support roller of the web support assembly is configured to support/guide the web independent of the interaction between the second web support assembly and the second web.

15. The web support assembly of claim 13, wherein the web support and the second web support assemblies are joined to a common base.

16. A web support assembly for supporting/guiding a substrate web comprising a multi-biasing arrangement configured so a surface of the web is biased along a first direction with a first bias force and the surface of the web is biased along a second direction with a second bias force, the second direction being substantially opposite the first direction.

17. The web support assembly of claim 16, wherein the multi-biasing arrangement is configured to have a biasing force transition zone between a web first position and a web second position where the web has a deflection within the biasing force transition zone that is substantially zero.

18. The web support assembly of claim 16, wherein the multi-biasing arrangement biases the surface of the web with a greater force along the first direction compared to a biasing force exerted upon the web along the second direction.

19. The web support assembly of claim 18, further comprising a roller, wherein the first bias force along the first direction reacts web movement into tie roller, and the second bias force along the second direction acts to maintain contact between the roller and web as the web moves away from the roller.

20. The web support assembly of claim 16, wherein the biasing arrangement includes a coil spring.