Gear cutting – milling – or planing – Planing – Means for cutting groove
Reexamination Certificate
2000-11-30
2002-07-23
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Planing
Means for cutting groove
C033S018100, C033S032300, C407S113000, C029S763000, C083S875000
Reexamination Certificate
active
06422793
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing a thin-film solar or photovoltaic module as well as to separating means for use in this process.
One possibility for producing thin-film solar modules or thin-film photovoltaic modules comprising a plurality of solar or photovoltaic cells disposed in parallel on a common substrate, which are produced and electrically interconnected by a plurality of cell-overlapping coating steps and coating-separation steps during cell production has already been described in U.S. Pat. No. 4,243,432. In that specification, CdS-Cu
x
S solar cells are produced in that a glass substrate is always completely provided with deposited individual layers, one upon the other. The layers in form of thin films mainly comprise a hard contact layer of SnO
x
serving as the lower electrode and a pn double layer of CdS-Cu
x
S disposed on it as well as a further contact layer serving as the upper electrode. Cuts performed between the individual thin film deposition steps have been provided to subdivide the cell-overlapping substrate film coating into individual cells, on the one hand, and to electrically series-connect the cells of a substrate, on the other hand. For serial interconnection of the cells, the cuts are provided such that the upper electrode of a cell
1
contacts the lower electrode of following cell
2
, however, is separated from the upper electrode of cell
2
. This scheme is continuously repeated over the whole substrate length. Various methods for separating the individual layers have been suggested in this US patent, inter alia by ultrasonic techniques, and it has been stated that the pn layer may also be separated for instance by means of a rotating or a non-rotating cutting tool.
In U.S. Pat. No. 4,315,096, a similar process has been disclosed for CdTe and CdS layers wherein the separation cuts having a width of between 5 &mgr;m and 100 &mgr;m are also produced either by mechanical methods not defined in detail or by means of laser beams. U.S. Pat. No. 5,501,744, also, refers to the production of CdTe and CdS solar cells. According to U.S. Pat. No. 5,501,744, the modules are processed by means of a tool head which is movable both in transversal and longitudinal direction relative to the substrate. The tool head includes lasers, arranged side by side, sandblast blowers or deposition means which are obliquely directed to the substrate and, preferably, do not contact the substrate. After processing the substrate in longitudinal direction, the head is displaced in transverse direction to a new starting position for longitudinal movement. During the course of this transverse movement, the processing units are not activated.
As yet, however, commercially traded silicon solar cell modules have not, as a rule, been fabricated in accordance with the above process of U.S. Pat. No. 4,243,432. Rather, they have been made of individual cells which are interconnected by means of soldered-on metal strips. Modules comprising CdS-Cu
x
S solar cells have not so far been produced on an industrial scale in accordance with the above-referenced process of U.S. Pat. No. 4,243,432. The same applies to CdS/CdTe solar cells which have, for a considerable time been considered as promising and which include a front contact of a transparent TCO layer, mostly in the shape of a so-called ITO layer. As to the production and the structure of such an individual solar cell, explicit reference is made to European Patent No. EP 0,535,522, which corresponds to U.S. Pat. No. 5,304,499.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a process for producing a thin film solar module which is characterized in that a scraping tool as cutting or separating means for the pn layer is used. Contrary to common cutting means, the cutting tool employed in accordance with the present invention includes a flattened tip and the plane flattened surface serves as sliding surface of the tool. During the separating process, the tool is guided so that it slides with its plane sliding surface on the first contact layer while the sliding surface rests with its complete flattened face on this layer which is in parallel to it. The longitudinal axis of the tool is in this case perpendicular to the contact layer, or the substrate, respectively. By this design and arrangement, the danger of damage to the contact layer by the plane sliding surface of the tool is reduced to a minimum. The adjustment of the pressing force exerted on the tool is substantially uncritical. The force may, without any danger, be adjusted at such a high value that the pn double layer is safely cut through. It is not necessary to provide for any sophisticated regulations and adjustments for the scribing or scraping depth of the tool. In addition, the tool may without any complicated adjustment be moved in any direction and may for instance follow a meander-shaped path without any need of being axially rotated before being forwarded to a new work area and before being moved in a new processing or cutting direction.
Contrary to the normally common technique of the application of non-rotating cutting tools such as raising and lowering tools, the cutting tool of the process according to the invention need not to be raised from the coated substrate, neither during the cutting process nor when shifting the tool to a new work area. By avoiding a time consuming raising and lowering of the tool on and from the front contact layer, respectively, it was possible to increase the life time of the cutting tool and to enhance the efficiency of the process.
It was an object of the present inventors to provide a process by which an efficient production of thin film solar modules is possible while making use of cell-overlapping thin film deposition and a rapid and safe separating technique. A further object was to develop suitable separating means for the production of thin film solar modules, which make such rapid and, at the same time, safe separation possible. Rapid separation is necessary because the separation steps are part of the continuous production process and cannot be decoupled from it. During the course of the separation process, in addition, it should be ensured that the desired layers are sufficiently completely cut through and separated while the layers or thin films disposed under them remain undamaged.
The prior art scribing tools which are drawn, in an inclined position and without a parallel sliding surface, over a substrate do not show the advantages described above. U.S. Pat. No. 4,502,225 uses a scribing tool which is moved under an oblique angle of preferably 75° relative to the horizontal (so-called back racking angle) over a substrate in order to separate silicon layers. The tool preferably includes a rounded diamond tip. As alternatives for the obliquely disposed tool, pyramid-like or truncated tips have been referred to. According to this US patent, the pressure adjustment of the tool and of its sharp scribing tip having a preferred diameter of about 0.01 mm is very critical. In order to obtain a defined scribing depth of the inclined tool rounded-off at the tip into the layer to be cut while not damaging the underlying layer, the pressing force is adjusted to tight limits using a complicated mechanical facility. One tries to monitor successful layer separation by means of resistance measurements, an action which can be ruled out in the case of electrically not conducting layers. After cutting a layer segment over the whole substrate length, the tool is raised and shifted into the new scribing position where it is lowered again. The oblique scribing tool shown can be moved in one direction only.
U.S. Pat. No. 4,589,194 shows also a scribing stylus guided in an inclined position relative to the substrate surface which as an alternative to the preferred diamond tip may optionally be produced completely of a hard metal. Amorphous silicon layers and back contact layers disposed thereon are cut. In order to avoi
Bonnet Dieter
Dinges Peter
Todisco Alexandra
ANTEC Solar GmbH
Cadugan Erica E
Quarles & Brady LLP
Wellington A. L.
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