DE102010042642B4 - Method and device for galvanic coating of substrates and solar cells - Google Patents

Abstract

Apparatus for the electroplating of substrates (1), - having a reservoir (12) which comprises an electrolytic coating liquid (13) and - comprising a lower transport device (40) and - an upper transport device (30) for the substrate (1) in which a transport device (30, 40) has means (20, 21, 24, 32) for contacting and connecting the substrate (1) to a voltage source (21), characterized in that at least one transport device (30) has at least one tampon ( 41) of an absorbent material (44) and in that means are provided so that the pad (41) receives the electrolytic coating liquid (13) and contacts the surface of the substrate (1) to be electroplated.

Description

The invention relates to a device for the galvanic coating of substrates according to the preamble of patent claim 1.

The invention also relates to a process for the galvanic coating of substrates and solar cells according to claims 9 and 10.

From the DE 10 2005 038 449 A1 is a device for the galvanic coating of substrates, in particular of solar cells, known, in which the solar cell between the upper and lower transport rollers are guided through an electrolyte bath. For electrical contact relief are also provided which come into contact with the substrates or abut against these. At this Kontaktierungsrollen also takes place a deposition, so that this raised from time to time, moved out of the electrolyte and must be freed from the coating. With this method, an all-round galvanization is possible. However, this method does not describe a partial front coating of a solar cell.

In the DE 10 2007 005 161 A1 describes a one-sided galvanization of solar cells, wherein also a partial electroplating of the solar cells is not possible with this method.

In the WO 2008/065069 A1 is the partial galvanization of printed circuits described, whereby via a roller contact conductor tracks can be partially galvanized. The disadvantage of this method, however, is that the complete contacting technique is immersed in an electrolyte liquid and the roller contacts as well as in the DE 10 2005 038 449 A1 at least partially co-coated. If the galvanic coating is carried out using light, the solar cell would be completely coated with this known method because the incident light would have a potential everywhere on the solar cell.

From the EP 0 003 680 A1 For example, there is known a device for tamponayerization which has a hand-operated electrode. The electrode has a handle, which is provided with a cloth of 75% polypropylene fibers and 25% nylon fibers, which is connected via an electrically conductive wire to the positive pole of a voltage source. The electrode is immersed with this cloth in an electrolyte and thus impregnated with this electrolyte. Subsequently, the electrode is contacted at the location of a substrate connected to the negative pole of the voltage source. Mass production is not possible with this device.

It is an object of the invention to provide a method and a device for the galvanic coating of substrates, in particular of solar cells, with which large quantities of substrates can be partially coated in a simple manner.

This object is achieved with a device according to the features of claim 1.

This object is achieved with a device for electroplating substrates, in particular solar cells, having a reservoir comprising an electrolytic coating liquid and comprising a lower transport device and an upper transport device for the substrate, wherein a transport device comprises means for contacting and connecting of the substrate to a voltage source. The device is characterized in that at least one transport device has at least one pad of an absorbent material and that means are provided so that the pad receives the electrolytic coating liquid and contacts the surface of the substrate to be plated.

The advantage of the device is that the substrate does not have to be immersed in the electrolytic coating liquid. An undesirable coating at locations other than the sites that are targeted and partially coated, such. As the tracks in solar cells, can be avoided. Through the use of tampons z. B. in a solar cell, a coating on a surface, in particular on the front, and there are only partially carried out in a simple manner.

Due to the fact that galvanic deposition takes place only where the pad contacts the surface of the substrate, structures such as printed conductors, in particular main printed conductors (busbars), in particular on the front side of solar cells, can be produced particularly advantageously. Busbare must have a certain thickness, which in conventional methods always with a corresponding widening of the busbar and therefore associated with an undesirable shading of the surface of the solar cell. Such shadowing leads to power losses of the solar cells. By Tampongalvanisierung structures, z. B. the printed conductors are applied directly to the substrate.

However, it is preferred that the structures, e.g. As the busbar, as previously applied by means of a paste or an ink-jet process and then selectively increase the thickness of the structures by means of Tampongalvanisierung, without widening the structures significantly.

The possibility of targeted post-processing of structures, such as busbars and / or contact fingers, is a considerable advantage over the known methods.

The device allows a continuous, partial coating of the substrates, whereby a cost-effective coating of a plurality of substrates and thus a mass production is made possible.

The dimensions of the tampon define the size of the contact surface and thus the size of the coated area on the substrate.

The absorbency of the material used for the tampon refers to the absorbency of electrolytic coating liquids. This absorbent material is preferably also flexible to z. B. via the contact pressure against the substrate to adjust the size of the contact surface or to remove after the contact the spent electrolyte liquid by compression from the tampon.

The negative pole of the voltage source is preferably electrically connected to the substrate via corresponding means of the upper transport device, in the case of a solar cell with the rear side.

The positive pole of the voltage source may be connected to an electrode which forms the anode and is in the coating liquid. Through the voltage source connected in this way, a galvanic current can be applied.

According to a further embodiment, the electrode may also be connected cathodically and the solar cell connected anodically. The electrode may be disposed at any position in the coating liquid. This assumes that during the coating process, the tampon both at least partially contacts the coating liquid and the substrate surface.

In addition to this possibility, there is also the option to connect the positive pole of the voltage source directly to the tampon or the carrier of the tampon. This alternative has the advantage that the impregnated tampon can be removed from the coating liquid and the electrodeposition can also be carried out outside the coating liquid.

The coating liquid is in a reservoir. This reservoir may be a container from which the coating liquid the tampon z. B. is supplied or immersed in the tampon, for example. A coating trough in which the coating liquid is located is preferred. The tampon plating has the advantage that a significantly lower amount of electrolytic coating liquid is required than in galvanic devices in which the substrate is immersed in the coating liquid.

The amount of coating liquid can be reduced to 1/6 to 1/10 of the usual amount. Conventional amounts of coating liquid in known galvanic coating plants for solar cells are in the range of 300 l to 500 l.

Vorzugsseise the transport devices lead the substrate at a distance over the coating tray. Coating pans are open at the top, so that during the Tampongalvanisierung dripping dripping coating liquid can be collected. In addition, the contact of the tampon with the coating liquid is facilitated.

The lower transport device preferably has at least one tampon. This tampon can be easily immersed in the coating liquid of the coating trough and subsequently or simultaneously brought into contact with the substrate surface. Also, coating liquid can be selectively supplied to the tampon from the coating tray, e.g. B. by means of pumps.

Preferably, at least one transport device, preferably the lower transport device, at least one transport roller or transport roller, which is provided with the pad of absorbent material or forms the tampon and thus consists of the absorbent material. The transport roller or the transport roller may have a base body of electrically conductive material which can be connected to the voltage source.

By means of such tampon rolls or pad rollers, the galvanic coating can be carried out continuously during unwinding of the roll or roller on the substrate, so that coated strips, such as. B. traces, can be easily produced.

In order for such a tampon roller to be able to contact the surface of the substrate without the substrate having to be immersed in a coating bath, this transport roller preferably partially dips into the coating liquid.

Preferably, the transport device, in particular the lower transport device, at least one conveyor belt, which is provided with the pad of absorbent material or forms the tampon and thus consists of the absorbent material.

Width and thickness and the cross-sectional shape of the tampon on the roll, roller or conveyor belt can be suitably selected according to the particular application. For example, square, rectangular, trapezoidal or triangular cross sections are possible.

The substrate to be coated rests on the conveyor belt during transport.

Preferably, the conveyor belt is a closed conveyor belt. About pulleys at the beginning and end of the transport route, the conveyor belt is guided. In this case, the conveyor belt at least partially immersed in the coating liquid.

Preferably, the conveyor belt, which may also be referred to as a tampon belt, guided in at least one guide element. This guide element can be arranged outside the coating liquid or outside the coating trough and / or in the coating liquid or in the coating trough. The guide element may be a guide rail. Such guidance of the conveyor belt increases the quality of the coating to the effect that, especially with a lateral guide, no lateral fluctuations or deviations can occur.

Preferably, the guide element is designed such that it can also absorb coating liquids. The supply of the guide element with coating liquid can be done for example by means of a feed pump which is connected to the reservoir.

At least one guide element can be electrically connected to the positive pole of the voltage source. The guide element forms the anode of the electroplating circuit.

The guide rail can for example also be designed U-shaped, wherein the two legs of the U preferably protrude. As a result, a channel is formed in which the leading conveyor belt can be guided. This channel can also be supplied with the coating liquid, z. By suitable supply means associated with the coating bath as a reservoir.

The coating liquid can flow down from the guide rail, for example at its open ends. If a coating trough is preferably arranged below the transport device, it can receive the used coating liquid from the guide element.

According to a further embodiment, at least one radiation source, in particular a light source, may be arranged in the coating liquid, preferably in the coating trough, for irradiating the surface to be coated. The light-assisted galvanic coating can significantly increase the deposition rate and thus the throughput of substrates.

In order that the electromagnetic radiation of the light source is as far as possible not completely shielded by the transport device, it is advantageous if the absorbent material for electromagnetic radiation in the range of 550 nm to 1200 nm has a transmittance of 0.05 to 0.2.

The absorbent material may be sponge rubber, polyester foam or polyurethane foam. Such materials have a very good suction and absorption capacity of electrolyte fluid, are wear-resistant and available in any dimensions. Even with small dimensions in the millimeter range, these materials are dimensionally stable.

The absorbent material preferably has 50 to 300 cells / cm ² . The cells of the material are optically determined by counting the pores (cells) in a given area.

Materials with this porosity have a high absorbency and guarantee even with small dimensions sharply contoured coating areas on the substrate.

According to the invention the object is achieved by a process for the galvanic coating of solar cells, wherein at least one surface of the solar cell is partially coated by means of a Tampongalvanisierungsverfahrens.

• – das Substrat wird an eine Spannungsquelle angeschlossen,
• – mindestens ein Tampon aus saugfähigem Material zur Aufnahme der Beschichtungsflüssigkeit wird mit der Beschichtungsflüssigkeit zusammengebracht,
• – der mit der Beschichtungsflüssigkeit getränkte Tampon wird mit dem Substrat kontaktiert, wobei an mindestens einer vorgegebenen Stelle auf der Oberfläche des Substrats Metall abgeschieden wird.

The object is also achieved by a process for the galvanic coating of substrates, in which an electrolytic coating liquid containing at least one metal is used, the process comprising the following process steps:

• The substrate is connected to a voltage source,
• - At least one pad of absorbent material for receiving the coating liquid is brought together with the coating liquid,
• - The impregnated with the coating liquid pad is contacted with the substrate, wherein at least one predetermined location on the surface of the substrate metal is deposited.

The substrate is preferably connected to the negative pole of the voltage source.

The positive terminal of the voltage source is electrically connected to an electrode in the coating liquid and / or the tampon.

The substrate is preferably arranged at a distance above a coating trough which comprises an electrolytic coating liquid comprising at least one metal.

The substrate is preferably moved over the coating trough at a distance. This enables a continuous coating by means of the Tampongalvanisierung and achieves a correspondingly high throughput.

The tampon may also partially contact the coating liquid during contact with the substrate. This means that a part of the tampon is immersed in the coating liquid and a part of the tampon protrudes from the coating liquid and contacts the surface of the substrate.

The tampon may also be completely outside the coating liquid. In this embodiment, the tampon is supplied with coating liquid from a reservoir.

Preferably, the substrate is coated along a predetermined path. This can be done for example with a roll on the substrate tampon roll or a tampon ribbon. This makes it possible to produce printed conductors of a solar cell.

The method provides that at least one surface of the substrate is coated directly with a structure. There is also the possibility of reinforcing or thickening existing structures. Preferably, the partial structures are conductor tracks of solar cells. These interconnects may preferably be busbar and / or contact fingers.

The surface to be coated can be irradiated continuously or discontinuously with light in the visible range during the coating process. Preferred is a pulsed irradiation. It is preferably used electromagnetic radiation in the range of 300 nm to 1200 nm, in particular in the range of 380 nm to 780 nm.

Exemplary embodiments will be explained in more detail with reference to the drawings. Show it:

1 a schematic representation of a coating bath with upper and lower transport means and a substrate.

2a a further schematic representation, which is a sectional view through the device according to 1 equivalent.

2 B a further schematic representation according to the 2a showing a cathodic circuit of the electrode.

3 and 4 show enlarged views of the transport rollers.

5 and 6 show in perspective and partially in section an overall device with conveyor belts.

In the 1 is a device for the galvanic coating of substrates 1 represented a reservoir 12 in the form of a coating tray 10 comprising an electrolytic coating liquid 13 located. In this embodiment, the substrate is 1 a solar cell 1a ,

The substrate 1 is between an upper transport device 30 and a lower transport device 40 arranged and is moved in the direction of the arrow. The two transport facilities 30 . 40 are arranged such that the substrate 1 above the upwardly open coating tray 10 located. The upper transport device 30 has upper transport rollers 32 of which only two are drawn. The substrate 1 owns on the back 2 a metallic coating 3 coming from the right top roller 32 contacted to the negative terminal of a voltage source 21 over the electrical connection line 24 connected. The positive pole of the voltage source 21 is via an electrical connection line 26 with an electrode 22 which forms the anode and in the coating pan 10 is arranged. Overall, a rectifier circuit is thus formed.

The lower transport device 40 has transport rollers 42 on that a reel body 43 that with an absorbent material 44 is occupied. In the illustration shown here, the axes of the lower transport rollers are approximately at the height of the bath level 14 , The roles 42 can also deeper into the coating liquid 13 immerse or further from the coating liquid 13 protrude. Because the lower transport rollers 42 equipped with the tampon similar to a tire, the tampon is at the same time partly in the coating liquid and partly outside.

An essential part of the lower transport rollers is the absorbent material 44 that the tampon 41 which forms the bottom of the substrate 2 contacted.

As absorbent materials based on rubber can be used: material Hardness [kg / m ³ ] Porosity [cells / cm ² ] ISO number (polymer) Sponge rubber HW 160 ± 40 50-300 1629

As absorbent materials on plastic / synthetic resin base can be used: material Density / density ISO 845 [kg / m ³ ] Compression hardness / compressive stress CV40; ISO 3386, 40% [kPa] Tensile strenght; ISO 3386 [kPa] Elongation at break; ISO 3386 [%] Compression set [%] polyester foam 40 ± 3% 4 ± 1 > 180 > 330 <10 PUR foam 18 to 77 6.5 ± 1.2 > 100 > 150 <5 Flexible polyether-based polyurethane foam 53 ± 8% 7 ± 1.1 140 150 3 Pu foam 18 to 77 2,7 to 11 100 to 120 150 to 180 ≤ 5 to 9 polyether 110 to 130 25 to 35 ≥ 200 ≥ 70 ≤ 3

As a mechanical property, the compressive strength according to ISO 3386-2 was chosen because it is a common measure for the characterization of foams and allows conclusions about the aging state of the material. The compressive stress in the fourth load cycle at 40% compression serves as a characteristic for the compression hardness.

The bulk density of the absorbent polymer materials is 18-130 kg / m ³ . The compressive strength / compressive stress is in the range of 2 to 35 kPa, the tensile strength is in the range of 100 to 300 kPa, the elongation at break in the range of 150-400% and the compression set in the range of 1-20.

In the 1 is the substrate 1 on the front side 4 already with tracks 5 provided, for example, have been applied in the form of a paste by means of an ink-jet process. Preferably, the conductor tracks are formed from silver or a silver alloy. The reworking shown here is about these prepared tracks 5 targeted by the Tampongalvanisierung thicker form without broadening them. Such interconnects may be the so-called Busbare, which can thus be thickened without broadening the conductor.

The role 45 is adjacent to the role 42 the lower transport device 40 arranged and also partially immersed in the coating liquid 13 one. The role 45 presses against the tampon 41 the role 42 so that it is squeezed out and then can absorb fresh electrolytic coating liquid.

In the 2a is a schematic sectional view of 1 to see, with the solar cell is connected anodically. There are two roles each 32 and 42 arranged side by side on a common axis. Because in the 2 a total of five tracks 5 are provided for post-processing of these interconnects and a correspondingly large number of lower transport rollers 42 with tampon 41 intended. For clarity, the other transport roles 42 not shown.

In addition, also schematically is still a light source 15 (here below the coating tray 10 drawn; in fact, the light source is in the coating tray 10 ), with which the front side 4 of the substrate 1 during the galvanic coating can be irradiated. This irradiation can be continuous or discontinuous.

In the 2 B is a cathodic circuit of the electrode 22 shown. The solar cell 1a is anodically connected, with the front 4 the solar cell 1a is contacted.

In the 3 another embodiment is shown, which is a lower transport roller 42 shows whose role body 43 with an absorbent material 44 is occupied. The substrate 1 does not have any tracks. These are immediately on the front 4 by means of the transport roller 42 applied almost completely in the coating bath 12 dips in and protrudes only slightly from the coating bath.

The backside 2 of the substrate 1 is to the rectifier circuit 20 connected, with the positive pole to the anode 22 connected to the coating bath 12 dips. As an alternative, which is shown in dashed lines, the positive pole of the voltage source 21 also with the lower transport roller 42 be connected.

The 4 shows a sectional view through the 3 , The light source 15 is between the two adjacent transport rollers 42 arranged.

In the 5 is a perspective view of a system with upper and lower transport device 30 and 40 represented, wherein the lower transport means circulating conveyor belts 46 having. The upper transport device has a plurality of transport rollers 32 while the lower transport means only two conveyor belts 46 has, with which two strip-shaped areas can be coated on a substrate.

In the 6 is an enlarged view to see. The conveyor belts 46 consist of a carrier belt 49 on which the tampon 41 is glued on. These conveyor belts 46 run over a pulley 48 and are in a guide element in the form of a U-shaped guide rail 50 guided, the above the coating tray 10 is arranged. The conveyor does not dip into the coating fluid 13 but the electrolytic coating liquid is introduced via supply pipes immersed in the coating bath 52 supplied with the electrolytic coating liquid. About these pipes 52 The electrolytic coating liquid is pumped 54 pumped into the U-shaped guide rails, in which the conveyor belt 46 the coating liquid 13 receives. The guide rails 50 are connected to the rectifier circuit 20 connected via electrical lines, not shown. The guide rails 50 form the anode 22 ,

LIST OF REFERENCE NUMBERS

1

substratum

1a

solar cell

2

back

3

metallic coating

4

front

5

conductor path

10

coating pan

12

reservoir

13

coating liquid

14

Bathroom mirror

15

light source

20

Rectifier circuit

21

voltage source

22

electrode

24

electrical connection line

26

electrical connection line

30

upper transport device

32

upper transport roller

40

lower transport device

41

tampon

42

lower transport roller

43

roller body

44

absorbent material

45

role

46

conveyor belt

48

idler pulley

49

carrier belt

50

Guide element, guide rail

52

supply pipe

54

pump

Claims (15)

Device for electroplating substrates ( 1 ), - with a reservoir ( 12 ) containing an electrolytic coating liquid ( 13 ) and - with a lower transport device ( 40 ) and - with an upper transport device ( 30 ) for the substrate ( 1 ), wherein a transport device ( 30 . 40 ) Medium ( 20 . 21 . 24 . 32 ) for contacting and connecting the substrate ( 1 ) to a voltage source ( 21 ), characterized in that at least one transport device ( 30 ) at least one tampon ( 41 ) of an absorbent material ( 44 ) and that means are provided so that the tampon ( 41 ) the electrolytic coating liquid ( 13 ) and the surface of the substrate to be electroplated ( 1 ) contacted. Apparatus according to claim 1, characterized in that the transport devices ( 30 . 40 ) the substrate ( 1 ) at a distance above the coating trough ( 10 ) to lead. Device according to one of claims 1 to 2, characterized in that the lower transport means at least one tampon ( 41 ) having. Device according to one of claims 1 to 3, characterized in that at least one transport device ( 30 . 40 ) at least one transport roller ( 42 ) or transport roller, with the tampon ( 41 ) of absorbent material ( 44 ) or the tampon ( 41 ) and from the absorbent material ( 44 ) consists. Device according to one of claims 1 to 4, characterized in that the transport device ( 30 . 40 ) at least one conveyor belt ( 46 ), which with the absorbent material ( 44 ) or the tampon ( 41 ) and from the absorbent material ( 44 ) consists. Apparatus according to claim 5, characterized in that the conveyor belt ( 46 ) in at least one guide element ( 50 ) is guided. Device according to one of claims 1 to 6, characterized in that in the coating liquid ( 13 ) at least one light source ( 15 ) for irradiating the surface of the substrate to be coated ( 1 ) is arranged. Device according to one of claims 1 to 7, characterized in that the absorbent material ( 44 ) consists of sponge rubber, polyester foam or polyurethane foam. Process for the galvanic coating of solar cells, wherein at least one surface of the solar cell ( 1a ) is partially coated by means of a Tampongalvanisierungsverfahrens. Process for the galvanic coating of substrates ( 1 ) in which an electrolytic coating liquid containing at least one metal ( 13 ), characterized in that the substrate ( 1 ) to a voltage source ( 21 ) that at least one tampon ( 41 ) of absorbent material for receiving the coating liquid ( 13 ) with the coating liquid ( 13 ) and that the impregnated with the coating liquid tampon ( 41 ) with the substrate ( 1 ) is contacted, wherein at least one point on the surface of the substrate ( 1 ) Metal is deposited. Method according to claim 10, characterized in that the positive pole of the voltage source ( 21 ) with an electrode ( 22 ) in the coating liquid ( 13 ) and / or with the tampon ( 41 ) is electrically connected. Method according to one of claims 10 or 11, characterized in that the substrate ( 1 ) at a distance above a coating trough ( 10 ) is moved. Method according to one of claims 10 to 12, characterized in that the tampon ( 41 ) during contact with the substrate partly also with the coating liquid ( 13 ) is in contact. Method according to one of claims 10 to 13, characterized in that at least one surface of the substrate ( 1 ) is coated directly with a structure. Method according to one of claims 10 to 14, characterized in that the surface to be coated during the coating process is irradiated continuously or discontinuously with light in the visible range.

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