DE102013100805B4 - Wet-chemical treatment plant for the electrochemical coating of flat substrates - Google Patents

Abstract

A wet-chemical treatment installation for the electrochemical coating of flat substrates (1) with coating material, with a basin for holding an electrolyte, and with transport means, with which the flat substrates (1) can be transported horizontally through the electrolyte, and with at least one contact element (2), which comprises a shaft (4) with a rotation axis (5) and a cylindrical circumferential surface suitable for rolling on the substrate (1), the peripheral surface comprising at least one electrically insulated segment (3B) and at least one electrically conductive segment (3A) a current source (6) is reversibly connectable, wherein the axis of rotation (5) of the contact element (2) is positioned above the surface of the electrolyte, and wherein the contact element (2) is designed as a consumption electrode.

Description

introduction

The invention relates to a device for metallizing substrates. In particular, the invention relates to the field of contact elements used for the galvanization of solar cells in the context of a wet-chemical continuous treatment plant.

State of the art and disadvantages

Substrates of semiconductor materials such as silicon require in the production of electronic components such. B. solar cells of at least one-sided coating with conductive materials such. B. copper. For this purpose, wet-chemical continuous flow systems ("inline systems") are used, among other things, through which the substrates are transported resting on transport rollers. During transport, the substrates are in contact with an electrolyte. For deposition of the metal contained therein, the substrates are poled cathodically.

For making the electrical contact between a power source and the substrate rolling contact wheels are known on the substrate. This is how the pamphlets reveal DE 44 13 149 A1 and DE 198 40 471 A1 Electroplating plants in which such contact wheels are used.

The problem here is the fact that not only the substrate, but also the conductive part of the contact wheel is metallized. Therefore, both documents cited above disclose the solution of segmenting the contact wheel and demounting the contact segment after leaving the surface of the substrate by reversing polarity. An improved solution for this is from the patent DE 10 2007 055 338 B4 known. Proposed are each arranged on a shaft pairs of contact wheels, which are driven out of phase, to ensure a continuous coating of the substrate. Contact wheels and the mandatory consumption electrodes are completely embedded in the electrolyte. In order to protect the contact wheels from coating, shielding hoods made of insulating material are proposed, which are each to be arranged between the contact wheel and the consumable electrode.

For example, the document discloses an alternative solution EP 0678 699 B1 , The sectorless contact rollers shown there, however, require auxiliary cathodes and semi-permeable membranes to achieve the desired effect, which complicates the design; In addition, the necessity of frequently changing the auxiliary cathodes is disadvantageous.

In practice, the realization of permanently functioning contact wheels has proven to be difficult.

Another problem arises from the high space requirement of the known contact wheels, which leads to correspondingly voluminous systems. In addition, completely immersed in the electrolyte contact wheels require complex solutions for extending and retracting the substrates in and out of the system, as significant differences in height are to be overcome by the fragile substrates.

The maintenance of the known systems with the contact wheels used there designed due to the high number of parts consuming.

Finally, it has also been shown in practice that the coating result often does not sufficiently homogenously precipitate.

Object of the invention and solution

The object of the invention is therefore to avoid the disadvantages mentioned above. The invention is intended to allow a robust, permanently functioning and low-maintenance electrical contacting of substrates to be metallized in wet-chemical continuous flow systems. An inventively designed system should be smaller compared to known systems. The maintenance is to be simplified and, if possible, the coating result should be improved.

The object is achieved by a treatment plant according to claim 1. Further advantageous embodiments are given in the dependent claims, the description and the figure.

description

A wet chemical treatment plant for the electrochemical coating of flat substrates with coating material which is suitable for the realization of the invention comprises a basin for receiving an electrolyte and transport means with which the flat substrates can be transported horizontally through the electrolyte. As a means of transport come in particular roller or roller-like transport means on which rest the substrates, into consideration. But also brackets on which the substrates are transported hanging, or attached to bands beams on which the substrates rest, are conceivable as a means of transport.

The treatment installation furthermore comprises at least one contact element, which has a shaft with an axis of rotation and a cylindrical circumferential surface suitable for unrolling on the substrate, wherein the peripheral surface comprises at least one electrically insulated segment and at least one electrically conductive segment which can be reversibly connected to a current source. Accordingly, the contact element is used for the electrical contacting of a substrate for the purpose of its electrochemical treatment (coating). The electrical contact between the power source and the substrate is made only when the latter is touched by the electrically conductive segment. Since the peripheral surface unrolls thereon during the continuous transport of the substrate, the conductive and insulated segments alternate.

The central angle of the electrically conductive segment is preferably between 90 ° and 270 °, and is particularly preferably 180 °. The remainder of the circumferential angle is associated with the electrically isolated segment.

While the conductive segment is cathodically connected during its contact with the substrate, thus allowing coating of the substrate, it is anodically switched upon non-contacting of the substrate, resulting in demetallization ("de-coating") of the segment. In this way, the thickness of a possibly deposited on the segment undesirable layer of coating material does not continue to, but (again) from; the net deposition of coating material is zero. When deviating from 180 ° Zentrivinkeln the electrically conductive segment, it is advantageous to the stripping performance by adapting z. As the current or the rotational speed to optimize.

According to the invention, it is provided that the axis of rotation of the contact element is positioned above the surface of the electrolyte. This means that at least half of the peripheral surface of the contact element is outside the electrolyte. The contact element is therefore not, as known from the prior art, completely immersed in the electrolyte. Stripping is still possible, since the peripheral surface when rotating about the axis of rotation carries electrolytes and also does not dry quickly, so that the anodic circuit of the electrically conductive segment leads to a discharge of the coating material, which is copper, for example, to the electrolyte.

Preferably, the distance between the axis of rotation and parallel to it to be contacted substrate side 80% to 100% of the radius of the peripheral surface. This means that only a small part of the peripheral surface is arranged in the electrolyte, wherein in the limiting case (100%) only a line contact between the peripheral surface and the surface of the electrolyte is possible. In this case, the substrate must be transported directly along the surface of the electrolyte, otherwise it may be correspondingly lower. Particularly preferably, the said distance is such that at least the shaft, and if possible also their bearings are arranged outside the electrolyte, unless they are beyond the pool wall, since in such a case there is no risk of damage by aggressive media anyway.

Such a treatment plant has the advantage that, because of the contact elements, which are arranged largely outside the electrolyte and are typically present in a plurality, they are more robust and durable and require less maintenance. The reason for this is the avoidance of the problems of storage and sealing of the contact elements within the electrolyte which occur in systems according to the prior art. The usually very aggressive media come no longer or only to a lesser extent in contact with the bearings, resulting in an improved life and easier construction of the same.

A further advantage is that a substrate is to be guided less deep below the surface of the electrolyte, regardless of the diameter of the overlying contact element.

According to the invention, the contact element is further configured as a consumable electrode. This means that it consists at least partially of coating material, so that it continuously emits coating material to the electrolyte with appropriate polarity, which then deposits on the substrate.

The advantage of a designed as a consumable electrode contact element is that such a contact elements comprehensive system can be built much smaller, as parts are saved.

Once the consumable electrode has delivered most of its coating material to the electrolyte, it can either be exchanged, or it can be cathodic poled with simultaneous introduction of new coating material introduced into or conveyed through the apparatus, for example in the form of substrate plates to be regenerated.

Due to the permanent loading and unloading of the consumption electrode, so the electrically conductive parts of the contact element, an oxidation of the same or is the same effectively prevented, so that a stable process with uniform deposition is achieved.

According to a preferred embodiment, the contact element as a pipe or rod of coating material, for. B. made of copper, and has along at least one provided for contacting the substrate longitudinal portion of its peripheral surface on an electrical insulating layer. However, this insulating layer may also extend to not provided for contacting the substrate longitudinal sections, if this is structurally advantageous.

This embodiment is structurally particularly simple and inexpensive to implement.

According to another embodiment, the contact element is designed as one or more discs, which are arranged on the shaft formed as a tube or rod.

In the case of a substantially tubular or rod-shaped contact element is preferred that the insulating layer is designed as a plastic part, which is attachable to the peripheral surface and this covers partially. The attachment can take place along the longitudinal axis (pushing), or it can be "clipped" laterally. If the central angle of the insulating segment is less than about 190 °, it is clear that precautions must be taken to hold the insulating layer to the pipe or rod otherwise it would fall off. Such precautions can z. B. sections with increased central angle, which are then located at locations which are outside the substrate track. But also plastic pins that cooperate with appropriately introduced into the tubular or rod-shaped shaft holes can serve the attachment. Preferably, the insulating layer is reusable.

According to a further embodiment, the shaft of the contact element for umpolbaren connection with the power source on a free, not provided for contacting the substrate longitudinal or end portion with the shaft with a rotatable sliding contact surface. This sliding contact surface cooperates with correspondingly arranged preferably fixed pins or the like, which in turn are connected to the poles of the current source and are preferably arranged outside the electrolyte.

The sliding contact surface is preferably configured disc-shaped and provided with two arcuate contact strips, which are designed according to the arranged on the peripheral surface segments. This means that their arc angles correspond to the two central angles of the segments and are arranged such that a polarity reversal takes place just when a segment change takes place at the substrate surface. It is clear that both contact strips are connected to the electrically conductive segment.

Particularly preferably, the sliding contact surface is arranged completely outside the electrolyte. This can be achieved, for example, by the fact that the basin wall has a corresponding passage through which the shaft can be guided. Thus, caused by aggressive media problems on the sliding contact surface on. If the shaft has a significantly smaller diameter than the peripheral surface, it is also possible to guide the shaft above the pelvic rim to the outside of the pelvis, or there is sufficient space between the lowest point of the sliding contact surface and the surface of the electrolyte so that there is no fluid contact is to be feared.

According to a further embodiment, the contact element is at the same time a hold-down device for avoiding the floating of the substrates. In other words, the contact element is designed and arranged such that it avoids floating of the flat substrate and its leaving the transport track. Hold-downs are known from the prior art, but are used exclusively for guiding the substrates, but not for electrical contacting.

In this way, again can be dispensed with components, resulting in a smaller and cheaper construction.

According to another combinable with the above embodiments, another embodiment, the contact element is at the same time a roller-shaped transport. In other words, the substrate rests on additional, then below the same positioned in the electrolyte contact elements, which lead by rotation to a continuous transport of the substrate through the basin.

Also in this way can be dispensed components, in the present case separate transport rollers, which also leads to a smaller and cheaper construction.

In certain cases, the replacement of the electrolyte in the area below the substrate - especially when there are contact elements - not be completely satisfactory, so that forms a not sufficiently homogeneous coating on the substrate bottom. Therefore, according to a further embodiment within the electrolyte of the continuous flow jet nozzles are also within the Electrolyte arranged parts of the contact element arranged with the electrolyte.

In other cases, it may happen that the above-mentioned wetting of the contact element during the phase in which the electrically conductive segment is outside the electrolyte is not completely satisfactory. Therefore, according to a further and preferred embodiment, outside of the electrolyte, that is, above its surface, there are arranged flow nozzles for the continuous wetting of the parts of the contact element, which are likewise arranged outside the electrolyte, with the electrolyte. In other words, the surge nozzles discharge the electrolyte originating from the basin, and / or, for example, also from a separate reservoir, in the direction of the contact elements, so that they are largely completely wetted. In this way, the construction can still be kept simple as described above, without questioning the success of the stripping.

The present invention solves the problems known from the prior art in a simple and effective manner. It allows a robust, permanently functioning and low-maintenance electrical contacting of substrates to be metallized in wet-chemical continuous flow systems. An inventively configured system is smaller compared to known systems. The maintenance is simplified, and the preferred embodiment of the invention improves the coating result.

figure description

In the 1 the invention will be explained schematically.

Accordingly, a flat substrate designed as a solar cell 1 arranged in an electrolyte (not shown). Its top is from a contact element 2 touched, more precisely from an electrically conductive segment 3A thereof. The shown, the touch of the substrate 1 serving peripheral surface of the contact element 2 is disc-shaped, but may also be cylindrical according to an embodiment not shown.

Opposite the electrically conductive segment 3A is an electrically insulated segment 3B arranged.

The contact element 2 has a wave 4 with rotary axis 5 on to the the contact element 2 and in particular the peripheral surface can rotate (arrow 7 ). The conductive and in contact with the electrolyte components (conductive segment 3A , Wave 4 ) consist at least partially of a material suitable for consumption and thus form a consumable electrode. As shown, in addition to the electrolyte of the invention is separate from the device according to the invention and with the power source 6 electrically connected consumable electrode 12 which, however, can advantageously be dispensed with according to a preferred embodiment which is not shown.

At one not for contacting the substrate 1 provided end portion 8th has the contact element 2 for umpolbaren connection with the power source 6 one with the shaft 4 with rotatable sliding contact surface 9 on. This is preferably arranged completely, but at least partially outside the electrolyte. This sliding contact surface 9 acts with appropriately arranged sliding contacts 10 together, which in turn with the poles of the power source 6 are connected.

The sliding contact surface 9 is presently disc-shaped and with two arcuate contact strips 11A . 11B provided, which correspond to the arranged on the peripheral surface segments 3A . 3B are designed. This means that their arc angles are the two central angles of the segments 3A . 3B are arranged and arranged so that a polarity reversal takes place just when a segment change takes place on the substrate surface. It is clear that both contact strips with the electrically conductive segment 3B are connected, which is present over the shaft 4 is reachable.

The contact strip 11A thus represents the contact area for the contact element stripping, and the contact strip 11B serves as a contact area for the substrate coating. Are not shown electrical lines from the contact strip to the conductive part of the peripheral surface or to the shaft.

LIST OF REFERENCE NUMBERS

1

substratum

2

contact element

3A

electrically conductive segment

3B

electrically insulated segment

4

wave

5

axis of rotation

6

power source

7

arrow

8th

not provided for contacting longitudinal or end portion

9

Sliding contact surface

10

sliding contact

11A

Contact strips

11B

Contact strips

12

consumable electrode

Claims (9)

Wet-chemical treatment plant for the electrochemical coating of flat substrates ( 1 ) with coating material, with a basin for receiving an electrolyte, and with transport means, with which the flat substrates ( 1 ) are transported horizontally through the electrolyte, as well as with at least one contact element ( 2 ), which is a wave ( 4 ) with rotation axis ( 5 ) and one for unrolling on the substrate ( 1 ) has a suitable cylindrical peripheral surface, wherein the peripheral surface at least one electrically insulated segment ( 3B ) and at least one electrically conductive segment ( 3A ) connected to a power source ( 6 ) is reversible connectable, wherein the axis of rotation ( 5 ) of the contact element ( 2 ) is positioned above the surface of the electrolyte, and wherein the contact element ( 2 ) is designed as a consumption electrode. Treatment plant according to claim 1, wherein the contact element ( 2 ) is designed as a tube or rod made of coating material and along at least one for contacting the substrate ( 1 ) provided longitudinal portion of its peripheral surface has an electrical insulating layer. Treatment plant according to claim 2, wherein the insulating layer is designed as a plastic part, which is attachable to the peripheral surface. Treatment plant according to one of the preceding claims, wherein the shaft ( 4 ) of the contact element ( 2 ) for umpolbaren connection with the power source ( 6 ) at one not for contacting the substrate ( 1 ) longitudinal or end portion ( 8th ) a sliding contact surface ( 9 ) having. Treatment plant according to claim 4, wherein the sliding contact surface ( 9 ) is disposed completely outside the electrolyte. Treatment plant according to one of the preceding claims, wherein the contact element ( 2 ) a hold-down to avoid the floating of the substrates ( 1 ). Treatment plant according to one of the preceding claims, wherein the contact element ( 2 ) is a roller-shaped transport means. Treatment plant according to one of the preceding claims, wherein inside the electrolyte flow nozzles for the continuous flow of the likewise disposed within the electrolyte parts of the contact element ( 2 ) are arranged with the electrolyte. Treatment plant according to one of the preceding claims, wherein outside the electrolyte flow nozzles for the continuous wetting of the likewise arranged outside of the electrolyte parts of the contact element ( 2 ) are arranged with the electrolyte.

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