The invention relates to a continuous deposition installation for the electrolyte deposition of a substance on objects as claimed in the preamble of claim 1, and to an assembly for a continuous deposition installation for the electrolyte deposition of a substance on objects.
If substances are intended to be deposited electrolytically on a large number of objects, then in many cases this can be realized advantageously in respect of outlay using continuous deposition installations. By way of example, metals or metal alloys can be deposited in large numbers on substrates, such as solar cell substrates or finished solar cells, for example, advantageously in respect of outlay on an industrial scale. Electrolyte depositions involve using an electrolyte containing ions of the substance to be deposited. Furthermore, a current flow is required, by means of which charge carriers can be fed to said ions, with the result that the ions deposit on the surface of the object. By way of example, in the case of a metal deposition, electrons are fed to an object surface to be coated, where they react with metal cations from the electrolyte upon contact with the electrolyte in a manner known per se and the metal is deposited on the object surface.
In order to deposit substances electrolytically on a large number of objects in continuous deposition installations, it is necessary to electrically contact the objects passing through the continuous installation. Since the objects move relative to the continuous installation, sliding contacts have proved worthwhile for this purpose. Such sliding contacts may be formed for example from electrically conductive brushes or at least partly elastically bendable sheets or films. In particular, films composed of metals, high-grade steel or else graphite can be used.
If a multiplicity of objects then pass through a continuous installation of the type in question, a sliding contact contacts firstly a first object and thereafter a further object subsequently passing through the installation. If, as customary or necessary in many applications, the objects then pass through the continuous installation at a certain spatial distance from one another, the sliding contact, after moving past the first object and before meeting the subsequent object, touches no object for a certain time. A direct contact between the sliding contact and the electrolyte often occurs during said certain time. By way of example, the sliding contact dips into an electrolyte solution. This is the case particularly during electrolyte deposition of substances on substrates such as solar cells, for example. This undesired direct contact between the sliding contact and the electrolyte then results in a deposition of the substance, for example the metal, from the electrolyte on the sliding contact. This effect occurs not only in the case of contact brushes, but also in the case of other contacting devices, such as metal rollers, for example. The undesired depositions on the sliding contact or other contacts may thereafter damage the surface of the subsequently contacted objects. In the case of thin objects, such as solar cell substrates or solar cells, for example, this may lead as far as the destruction of the object. Moreover, corrosion phenomena may occur at the contacts.
Against this background, the problem addressed by the present invention is that of providing a continuous deposition installation for the electrolyte deposition of a substance on objects by means of which the electrolyte deposition of substances on contacting devices can be reduced or even avoided.
This problem is solved by means of a continuous deposition installation having the features of claim 1.
Furthermore, the invention addresses the problem of enabling such continuous deposition installations to be manufactured advantageously in respect of outlay.
This problem is solved by means of an assembly having the features of claim 9.
Dependent subclaims respectively relate to advantageous developments.
The continuous deposition installation according to the invention for the electrolyte deposition of a substance on objects comprises contacting devices having at least one electrically conductive contact arm. Furthermore, the contacting devices are arranged in those regions of the continuous deposition installation which are free of an electrolyte used for the electrolyte deposition of the substance. On account of this arrangement, a direct contact between the contacting devices and the electrolyte occurs neither at times when the contacting devices contact the objects nor at times when they contact no objects. The undesired electrolyte deposition of the substance on the contacting devices is thus avoided. Rapid or premature corrosion of the contacting devices is prevented and stabler process conditions for the deposition process result. Furthermore, the process control can be greatly improved. Furthermore, the maintenance outlay for the continuous deposition installation can be reduced since the contacting devices do not have to be cleaned of undesirably deposited substance, which would otherwise have to be done by etching or reversing the current direction after a certain time. Moreover, the possibility of using a higher electric current density is afforded in many cases.
The contact arm is preferably embodied in a flexible fashion. Unevennesses on the object surface can be overcome advantageously in respect of outlay in this way. Preferably, a plurality of contact arms are provided since a reliable contacting by means of the contacting devices can be realized in this way, even in the case of uneven object surfaces.
The contact arms, or the entire contacting device, can be fabricated for example from graphite film or high-grade steel sheet, wherein a thickness of approximately 0.5 mm has proved worthwhile in the case of high-grade steel sheet. A coating of the contact arms, for example with a noble metal such as gold, may be advantageous in an individual application.
Preferably, use is made of contacting devices whose contact arms, at least in those regions in which they contact the objects, have smooth edges. Such smooth edges can be realized for example by laser cutting, wire erosion or electropolishing. Owing to the use of contact arms having smooth edges, the risk of scratches or other damage of the object can be avoided or at least reduced.
Preferably, all contacting devices are arranged in a region free of the electrolyte. The advantages of the invention can be utilized to the greatest possible extent in this way.
In principle, however, there is also the possibility of arranging one or more contacting devices in a different way.
In one advantageous configuration variant, the electrolyte is arranged in a tank. At least one outflow device is provided in the tank, by means of which at least one outflow device the level of the electrolyte is able to be locally reduced in outflow regions. The contacting devices have contact surfaces, by means of which the objects are contactable. These can be for example simply those surfaces of the at least one electrically conductive contact arm which make contact with the object during the operation of the continuous deposition installation. Said contact surfaces of the contacting devices are arranged in said outflow regions. In this way, the feature according to which the contacting devices are to be arranged in regions of the continuous deposition installation which are free of the electrolyte can be realized advantageously in respect of outlay.
Preferably, at least one outflow device comprises a hollow body, which is arranged at least in sections below the contact surfaces of at least one contacting device and through which the electrolyte is able to flow at least in sections. The hollow body can be shaped and arranged such that it is situated only below the contact surfaces of a single contacting device. Alternatively, there is the possibility of dimensioning the hollow body such that it is situated at least in sections below the contact surfaces of a plurality of contacting devices. In this way, the outflow regions can be adapted to the position of the contact surfaces, and vice versa, particularly advantageously in respect of outlay.
Particularly preferably, the at least one outflow device has at its top side an opening arranged at least partly below the level of the electrolyte. This makes it possible to lower the level of the electrolyte in a highly localized manner.
In practice, it has proved worthwhile to provide a pipe as hollow body, the upper opening of which pipe is arranged below the contact surfaces of at least one contacting device.
In one configuration variant, a plurality of contacting devices, preferably all contacting devices, are electrically conductively connected to the same voltage source. They are thus fed via this voltage source. This enables cabling of the contacting devices that is advantageous in respect of outlay. However, dissimilar deposition rates may be established at the contacting devices. This is attributable to the fact that in part significantly different electrical resistances are present on the path from the voltage source to the respective contacting devices. In order to compensate for this, provision is made for a load resistance to be connected upstream of at least one portion of the plurality of contacting devices. In this case, the respective load resistance is dimensioned such that upon contact being made, an electric current of substantially identical magnitude is applied to each of said plurality of contacting devices. In other words: the load resistances are chosen such that the described differences in electrical resistance on the path from the voltage source to the respective contacting device are compensated for and the same electric current flows through each contacting device. Contact being made in the present sense should be understood to mean that the contact surfaces bear against the object in such a way that an electric current can flow. If all contacting devices are connected to the voltage source, a central voltage supply is possible, and all contacting devices are connected in parallel. Conflicting with the advantages described is an increased installation outlay since it is necessary to determine and compensate for the differences in resistance for the individual contacting devices. Moreover, a higher electrical power loss is established, such that the voltage source has to provide significantly higher voltages, which can increase the apparatus outlay for the production of the continuous deposition installation.
Alternatively, a dedicated rectifier can be provided for each contacting device. Said rectifier is preferably embodied as a constant-current source. The determination and installation of load resistances compensating for differences in resistance can be avoided or at least reduced in this way. However, with this procedure, in the case of an industrial continuous deposition installation that is customary at the present time for solar cell fabrication, approximately 250 rectifiers or constant-current sources would be required. This necessitates a considerable space for installation, which must generally be provided outside the actual continuous installation. Moreover, a high cabling outlay arises for installations dimensioned in this way.
The assembly according to the invention for a continuous deposition installation for the electrolyte deposition of a substance on objects comprises at least one contacting device, and also a control device connectable to a voltage supply. Each of the at least one contacting device is connected to the control device via separate electrical lines, such that electric current is able to be applied separately to each of the at least one contacting device. By means of such an assembly, the continuous deposition installation described above can be constructed modularly.
Preferably, the at least one contacting device comprises a plurality of contacting devices, preferably at least four contacting devices. This makes it possible to realize the above-described advantages of constant-current sources for each contacting device more advantageously in respect of outlay.
Accordingly, the control device is advantageously configured to the effect that electric current applied to the individual contacting devices of the at least one contacting device is controlled by open-loop control and/or closed-loop control separately for each of said individual contacting devices. Measurement variables used for closed-loop control processes, such as, for example, current flow through the respective contacting device or contact resistances at the respective contacting devices, can be recorded in process histories and the further process for each object can be optimally adapted to each contacting device or other process locations.
Preferably, the control device is configured as constant-current closed-loop control for each individual contacting device of the at least one contacting device such that electric current of constant magnitude is able to be applied separately to each individual contacting device of the at least one contacting device. In this way, a uniform electrolyte deposition of substances in electrolytic continuous deposition installations can be realized comparatively advantageously in respect of outlay.
Advantageously, the control device is configured to run through separate, predefinable current profiles for each individual contacting device of the at least one contacting device. In this case, a current profile should be understood to mean a temporally variable sequence of values of electric current. The term run through means that values of electric current which correspond to the current profile are applied to the affected contacting device in temporal succession. In this case, said values of the electric current can be controlled by open-loop control or closed-loop control. This configuration of the assembly affords enhanced process engineering possibilities. By way of example, current pulses can be applied to the contacting devices, and thus to the objects contacted by the latter in a continuous deposition installation. In English-speaking areas, this procedure is referred to in some instances as pulse plating. In addition, it is possible to apply currents of reverse or alternate polarity, which in some instances in English linguistic usage is referred to as reverse plating. Delays or pauses in deposition processes are also able to be realized.
In one advantageous configuration variant, the control device has a communication interface, by means of which data are exchangeable bidirectionally with a data processing device. In this case, said communication interface is preferably embodied as a bus interface, for example as an interface of a CAN bus. By means of the communication interface described, the current control device can obtain stipulations for the current control from the data processing device. Furthermore, it is possible to communicate measurement data determined by the control device, for example current flows at individual contacting devices, to the data processing device for the purpose of process monitoring and archiving of process data, and they can be stored for example at said data processing device. This makes it possible, inter alia, to compensate for deficiencies established in the course of the process in subsequent installation regions by means of adapted process parameters. Data exchange via the communication interface is preferably effected by way of a protected protocol.
The continuous deposition installation according to the invention preferably comprises at least one of the assemblies described above. In this way, the advantages thereof can be made usable in the continuous deposition installation.
The continuous deposition installation described in the present case can advantageously be used for the electrolyte deposition of metals or metal alloys. Particularly advantageously, it can be used during the electrolyte deposition of metals or metal alloys on a substrate, in particular on a solar cell.
In practice, the continuous deposition installation according to the invention has proved worthwhile in the metallization of solar cells with what is often referred to in English linguistic usage as aluminum back surface field, in the metallization of passivated emitter and rear solar cells, so-called PERC cells, in the metallization of passivated emitter rear totally diffused solar cells, so-called PERT solar cells, and in the metallization of solar cells that are sensitive to light on both sides, so-called bifacial solar cells.
The invention is explained in greater detail below with reference to figures. In so far as expedient, identically acting elements are provided with identical reference signs herein. The invention is not restricted to the exemplary embodiments illustrated in the figures—not even with regard to functional features. The description above and also the description of the figures below contain numerous features which are rendered in part as a plurality in combination in the dependent subclaims. These features and also all the other features disclosed above and in the description of the figures below will, however, also be considered individually and combined to form expedient further combinations by the person skilled in the art. In particular, all features mentioned are combinable in each case individually and in any suitable combination with the continuous deposition installation and the assembly as claimed in the independent claims.
In the figures:
The continuous deposition installation 10 comprises contacting devices 12. The latter are illustrated with only one electrically conductive contact arm 13 in
The contacting devices 12 have contact surfaces 14 at their lower end. These are those surfaces of the contacting devices 12 which make contact with the surface of the solar cells 1 as the solar cells 1 pass through the continuous deposition installation 10. Said contact surfaces 14 of the contacting devices 12 are arranged in the outflow regions 18. Consequently, the contact surfaces 14, and thus the contacting devices 12 in their entirety, even when they are currently not bearing on one of the solar cells 1, do not make contact with the electrolyte 7. Consequently, the contact surfaces 14 and likewise the contacting devices 12 in their entirety never make contact with the electrolyte 7 and the disadvantageous deposition of metal on the contacting devices 12 as described above is avoided. At those moments when the solar cells 1 are being transported through below the contacting devices 12 and being contacted by the contact surfaces 14, it may indeed happen, depending on the dimensioning of the pipes 16, that the contact surfaces 14 bearing on the surface of the solar cells 1 are situated outside the outflow regions 18. Nevertheless, since the contact surfaces 14 lie above the level 8 of the electrolyte 7 at these moments, no contact arises between the contact surfaces 14 or other parts of the contacting devices 12, on the one hand, and the electrolyte 7, on the other hand.
In the exemplary embodiment in
The second exemplary embodiment illustrated in a schematic sectional illustration in
In the case of the continuous deposition installation 30, all contacting devices 32a, 32b are electrically conductively connected to a voltage source 40. For the purpose of compensating for differences in the electrical resistance as described in greater detail above, load resistances 38 are connected upstream of all contacting devices 32a, 32b. In the exemplary embodiment in
As in the other exemplary embodiments illustrated in the figures, the solar cells 1 are transported in the transport direction 3 by means of the transport rollers 4 and are guided past the contacting devices 32a, 32b in the process. In this case, the contacting devices 32a, 32b, formed from a high-grade steel sheet in the exemplary embodiment in
The continuous deposition installation 50 comprises four assemblies 60. The number of assemblies can be increased or decreased as necessary. Each of said assemblies comprises three contacting devices 52 in the exemplary embodiment in
Besides the contacting devices 52, the assembly 60 comprises a control device 64 connectable to a voltage supply. Said control device is already connected to the voltage supply 70 owing to the use of the assembly 60 in the continuous deposition installation 50 in the illustration in
Furthermore, the assembly 60 comprises a data processing unit 68 configured to carry out measurement processes within the assembly, for example current or resistance measurements at individual contacting devices 52 or contact arms 53a, 53b, 53c, and to detect measurement values and to process them further as necessary. The control device is configured as constant-current closed-loop control for each contacting device. Furthermore, the control device is configured to run through separate, predefinable current profiles for each contacting device 52. The stated functions of the control device can be realized by means of discrete electrical or electronic circuits or components. Preferably, the data processing unit 68 is configured to provide these functionalities, if appropriate with recourse to further components of the control device 64. This enables a high flexibility in the process management. This flexibility is additionally intensified by the bus interface 66 provided in the assembly 60, said bus interface enabling bidirectional data exchange with a data processing device 72. Using said bus interface, measurement data determined by the control device 66 can be evaluated in the central data processing device and the assemblies 60 arranged downstream in the transport direction 3, or the contacting devices of said assemblies, can be driven in a targeted manner for each individual solar cell. This makes it possible to compensate for or at least reduce ascertained shortcomings by adapting the process parameters in subsequently traversed parts of the continuous deposition installation 50 or to adapt the process parameters to individual properties of the respective solar cell 1. Moreover, for the purpose of process archiving, measurement and process data for each treated solar cell can be communicated to the data processing device 72 and archived.
Complex current profiles can be realized by means of the data processing unit 68. By way of example, it is possible firstly to use low current values in order that possible electrolyte splashes present on the solar cells can dry and sparking is avoided. At a later point in time in the course of the process, higher currents can then be provided in order to realize required deposition rates.
In all exemplary embodiments shown in the figures, components worthy of protection can be protected against corrosion, if necessary, by means of a protective lacquer or potting in epoxy resin.
Although the invention has been illustrated and described more specifically in detail by means of preferred exemplary embodiments, the invention is not restricted by the exemplary embodiments disclosed and other variants of the invention can be derived by the person skilled in the art, without departing from the basic concept of the invention.
Number | Date | Country | Kind |
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10 2016 124 002.8 | Dec 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/DE2017/101049 | 12/8/2017 | WO | 00 |