The invention relates to a method and an apparatus for providing a solar cell, also called photovoltaic cell, with a solder ribbon.
In order to manufacture solar modules that may, for example, be placed on a roof of a building for solar energy generation, several solar cells with bus bars are typically connected in series with each other to form so-called strings. For this, bus bars of the solar cells are series-connected with the bus bars of neighboring solar cells by solder ribbons. A solder ribbon is thereby connected to the positive terminal of a solar cell and to the negative terminal of the neighbouring solar cell, i.e. the solder ribbon is alternatingly connected with the lower side of one solar cell and with the upper side of the neighboring solar cell. The solder ribbons are typically made of tinned copper and are connected with the bus bars by one or more soldering units. A solar cell can have several bus bars, in particular between one to three bus bars, which arrangement requires an equal amount of solder ribbons for forming a string. The strings are formed in an apparatus called stringer.
After the solar cell strings have been formed, they are typically transferred to a quality testing station for inspection of the alignment of the solar cells and the solder ribbons, as well as for the detection of possible breakage. Then the strings are placed next to each other and cross-linked to obtain a solar cell matrix. After the cross-linking, the solar cell matrix is laid sun-side down upon a glass plate with an adhesive layer and covered with a glass or plastics cover having an adhesive layer. Then the matrix is laminated in a laminator for protection purposes.
For facilitating the soldering when the solar cells are connected with the solder ribbons to form the strings, flux is typically employed as chemical cleaning agent to remove oxidation from the metals to be joined and to prevent the formation of metal oxides. Furthermore, the provision of flux allows the solder to flow easily rather than to form beads. The flux is usually provided by the solder ribbon or the solar cell running through a flux bath or by applying the flux to the solder ribbon with a brush or a spray head with the entire solder ribbon being brushed. The known methods have the disadvantage that the flux does not only come to lie on the bus bars but often also on the semiconductor material of the solar cells, which might cause damage to solar cells and might impair the laminating process of the solar modules formed from the solar cells. In such a case, the flux might evaporate over time, even when inside a solar panel.
The invention relates to the context of providing a process and an apparatus for providing a solar cell with a solder ribbon, by which these above disadvantages and/or others may be avoided. In aspects, the invention also relates to the context of providing a method and an apparatus for providing a solar cell with a solder ribbon, by which the fluxing and soldering process may be expedited. In further aspects, the invention also relates to the context of providing a process and an apparatus for providing a solar cell with a solder ribbon, by which the amount of required flux may possibly be reduced.
In order to seek these or still further advantages by implementations of the invention, as shall become more readily apparent as the description proceeds, a process for providing a solar cell that has at least one bus bar with a solder ribbon is provided, wherein flux is applied by at least one automatically controlled spray head, and the solder ribbon is connected to the bus bar by at least one automatically controlled soldering unit. The flux may be applied only to those locations of the solder ribbon that shall be connected to the bus bar by the one or more soldering units. Alternatively or additionally, the flux may be applied only to those locations of the bus bar that shall be connected to the solder ribbon by the one or more soldering units, i.e., the locations of the applied flux correspond to/correlate with the locations at which the solder ribbon is soldered after application of the flux.
A version of the apparatus may include at least one automatically controlled spray head for applying flux and at least one automatically controlled soldering unit for connecting a solder ribbon to a bus bar. The spray head may be controlled such that the flux is applied only to those locations of the solder ribbon that shall be connected to the bus bar, by the one or more soldering units when the apparatus is operated. Alternatively or additionally, the spray head may be controlled such that the flux is applied only to those locations of the bus bar that shall be connected to the solder ribbon by the one or more soldering units when the apparatus is operated. A control unit may be provided for controlling the at least one spray head. It may form part of the spray head.
In versions thereof, the process and the apparatus have the advantages that less flux is required and that the fluxing and soldering process may be performed faster than with the above-mentioned known methods and corresponding apparatuses. The process and the apparatus may of course also be applied if the solar cells have several bus bars, wherein each bus bar shall preferably be connected with a solder ribbon.
Preferably, a preheating unit may be provided for preheating the solder ribbon and/or the bus bar, so as to reduce the amount of alcohol in the flux and/or to activate the flux. For the preheating, the preheating unit may employ any kind of heating mechanism/technology such as a laser, a heat die, a soldering iron and/or the provision of heated air. The preheating unit and hence the temperature it provides are preferably controllable. If the solder ribbon and the bus bar shall be connected by wet soldering, the preheating unit is preferably controlled such that the temperature it generates is less than 80 degrees Celsius so that relatively little solvent, e.g. alcohol, is evaporated from the flux. If the solder ribbon and the bus bar shall be connected by dry soldering, the preheating unit is preferably controlled such that the temperature it generates is equal to or higher than 80 degrees Celsius so that a relatively large amount of alcohol is evaporated from the flux and the amount of solvent is thereby reduced. By setting the temperature that the preheating unit generates equal to or higher than 100 degrees Celsius, the flux may be activated, whereas if the temperature the preheating unit generates remains lower than 100 degrees Celsius, activation of the flux typically does not occur. The preheating unit may comprise a soldering tip, a laser, a unit for generating ultrasound and/or a unit for generating hot air, among others. The actual connecting of the solder ribbon to the bus bar by soldering takes place by a temperature of approximately 100 to 120 degrees Celsius. During the soldering, preferably just the areas of the solder ribbon and/or the bus bar may be heated, onto which flux has been previously applied. Alternatively, an elongated area of the solder ribbon and/or the bus bar may be heated, that includes the areas onto which flux has been applied, wherein the direction of elongation corresponds to the longitudinal extension of the solder ribbon and/or the bus bar. In this latter case, soldering mainly takes place at the locations onto which flux has been applied.
Preferentially a monitoring unit is provided that preferably comprises a camera, preferably a camera that can take range images, i.e. 3D-images. A 2D-camera or a line sensor may also be used. The monitoring unit monitors the position of the bus bars so that the position of the one or more spray heads may be controlled and corrected by the control unit in dependence on the monitored positions of the bus bars to ensure that the flux is applied to those locations on the bus bars that shall be connected to solder ribbon, i.e. to the “correct” locations. The monitoring by the monitoring unit may be done before the flux is actually applied for process control and/or after the flux is actually applied for quality inspection.
The monitoring unit furthermore preferably detects and monitors the actual locations on the solder ribbon and/or the bus bar on which the flux is or has been, respectively, applied by the one or more spray heads. These monitored actual locations of the flux are then compared by the monitoring unit or a control unit with those predetermined locations of the solder ribbon and/or the bus bar that shall be connected to the bus bar and/or the solder ribbon by the one or more soldering units. If there is a difference between the monitored actual locations to which flux has been applied and the predetermined locations that shall be connected by soldering, then the position of the one or more spray heads is controlled by a control unit such that this difference converges to zero or is at least minimized.
If the one or more spray heads are wider than a bus bar and/or a solder ribbon, onto which flux shall be applied, and comprise a set of spray nozzles that are arranged in an array, then the control unit is preferably configured so that it can control the one or more spray heads to disperse flux from a subset of spray nozzles arranged in an area that is not wider than the bus bar and/or the solder ribbon.
Further advantageous features and applications of versions of the invention shall become evident from the remaining disclosure, the following description of the drawings illustrating the invention, and the drawings. In the drawings like reference signs designate the same or similar parts throughout the several figures, in which:
In the versions 8, 9 shown in
In a second step 20 the temperature provided by the preheating unit 11 may be set to a second predefined temperature that preferably is equal to or higher then 100 degrees Celsius if activating of the flux is desired before the actual soldering starts. Alternatively, the second predefined temperature may be given by the first predefined temperature, if the first predefined temperature is smaller than 100 degrees Celsius; or, it may be set to a temperature below 100 degrees Celsius if activation of the flux shall first occur with the soldering. In step 20 the preheating preferably also occurs only at those locations of the solder ribbon and/or the bus bar that shall be subsequently connected by soldering.
In a third step 30 the flux is applied by the one or more spray heads 5,6 to the solder ribbon and/or the bus bar with specific flux drop sizes and/or in specific patterns, as described previously with regard to exemplary showings in
In a fourth step 40, the solder ribbon and the bus bar are then soldered together by one or more soldering units 41 at the predetermined locations.
The steps 10 and 20 are optional, wherein either both steps 10 and 20, only step 10 or only step 20 or neither step 10 nor step 20 may be performed. Furthermore, it is preferably monitored by a monitoring unit 16 if those locations onto which flux is applied actually correspond to those predetermined locations that shall be soldered. If such is not the case, the position of the one or more spray heads 5,6 is corrected as described previously.
In closing, it should be noted that the invention is not limited to the abovementioned versions and exemplary working examples. Further developments, modifications and combinations are also within the scope of the patent claims and are placed in the possession of the person skilled in the art from the above disclosure. Accordingly, the techniques and structures described and illustrated herein should be understood to be illustrative and exemplary, and not limiting upon the scope of the present invention. The scope of the present invention is defined by the appended claims, including known equivalents and unforeseeable equivalents at the time of filing of this application.
Number | Date | Country | Kind |
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09011796 | Sep 2009 | EP | regional |
This application is a Continuation-In-Part (CIP) of copending PCT International application no. PCT/IB2010/054146 filed on Sep. 14, 2010 and published as WO2011/033451A2 on Mar. 24, 2011, which in turn claims benefit of priority to prior European application EP 09011796 filed on Sep. 16, 2009; the entirety of parent PCT International application no. PCT/IB2010/54146 is hereby expressly incorporated herein by reference, in its entirety and as to all its parts, for all intents and purposes, as if set forth identically in full herein.
Number | Date | Country | |
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Parent | PCT/IB2010/054146 | Sep 2010 | US |
Child | 13421800 | US |