CONTACTING DEVICE

Abstract

The present invention relates to a device for contacting a wafer during submersion in a liquid. The device comprises a main body fixed to a transportation device; an electrical contact for contacting the wafer and a pressure element for pressing the electrical contact towards the wafer.

Description

FIELD OF THE INVENTION

The present invention relates to a device for contacting a solar cell wafer.

BACKGROUND OF THE INVENTION

In UK patent application 0709619.1 it is described a device for exposing a solar cell wafer to a liquid, comprising a container filled with the liquid; a transportation device for transporting the wafer through the liquid; and a carrier device for carrying the wafer together with the transportation device.

In UK patent application 0719805.4 it is shown a device for supplying electrical power to a wafer that is at least partially submerged in a liquid, comprising a liquid container filled with the liquid; a transportation device comprising a wafer carrier device for transporting the wafer at least partially submerged through the liquid; and a power supply device for supplying electrical power to the wafer.

These publications are for example used in electroplating processes where for example Ni, Cu, Sn and/or Ag is applied to the wafer.

A challenge in this process is to provide electrical contact to the wafer without applying strong mechanical forces to the wafer, which may cause breakage of the wafer. Moreover, it is a need to improve the speed of the process for large scale production of solar cells. In electroplating, this is done by increasing the current density applied to the wafer since the number of metal atoms deposited on the wafer surface is directly proportional to the current applied to the wafer. However, there is an upper limit for the current density called the limiting diffusion current density I_L (I_L=(nFD_oxc_b)/δ). (ref. page 97 M. Paunovic and M. Schlesinger, Fundamentals of Electrochemical Deposition Second Ed., pp. 97, John Wiley and Sons, 2006). I_L is the value of the current where mass transport of ions to the electrode/solution interface start to become the limiting factor for the overall rate of reaction. By increasing the agitation at the solution/electrode interface, the Nernst diffusion layer, δ, becomes smaller. In turn, this implies that I_L increases and the theoretical deposition rate of metal can be increased.

The object of the present invention is to improve the electrical contact to the wafer so the above conditions can be met. In particular, the device enables turbulent agitation from the same side as the contacts are applied to the wafer, while at the same time wafers continuously are moving forward through the process.

SUMMARY OF THE INVENTION

The present invention relates to a device for contacting a wafer during submersion in a liquid, comprising:

• • a main body fixed to a transportation device;
  • an electrical contact for contacting the wafer;
  • a pressure element for pressing the electrical contact and the wafer towards the wafer.

In an aspect of the invention, the electrical contact is provided on the pressure element.

In an aspect of the invention, the pressure element is movably connected to the main body.

In an aspect of the invention, the pressure element comprises a floating element.

In an aspect of the invention, the main body comprises a groove adapted to receive an end of the wafer.

In an aspect of the invention, the electrical contact comprises an upwardly protruding contact.

In an aspect of the invention, the upwardly protruding contact is connected to a bus connector for connection to a bus bar.

In an aspect of the invention, the upwardly protruding contact is connected to the bus connector by means of an electric wire.

In an aspect of the invention, the device comprises several independently movable pressure elements having independent floating elements.

DETAILED DESCRIPTION

Embodiments of the present invention will now be described in detail with reference to the enclosed drawings, where:

FIG. 1 shows a perspective view of three holding devices holding two wafers;

FIG. 2 shows a side view of FIG. 1;

FIG. 3 shows an enlarged side view of one of the holding devices in FIG. 2;

FIG. 4 shows a perspective view from below of one of the holding device in FIG. 4;

FIG. 5 shows a side view of the holding device in FIG. 2, where some parts are omitted;

FIG. 6 shows a perspective view of the holding device in FIG. 5;

FIG. 7a shows a perspective view of a second embodiment of the holding device;

FIG. 7b shows a side view of the second embodiment;

FIG. 7c shows the floating element of the second embodiment;

FIG. 7d shows a front view of the second embodiment;

FIG. 8a shows a perspective view of a third embodiment of a holding device and bus bar;

FIG. 8b shows a side view of the holding device and bus bar in FIG. 8a;

FIG. 8c shows a front view of the holding device and bus bar in FIG. 8a;

FIG. 8d shows a perspective view of the third embodiment, where the main body is removed;

FIG. 8e shows a front view of the main body;

FIG. 9 shows a semi-transparent perspective view of a fourth embodiment;

FIG. 10a shows a semi-transparent perspective view of a fifth embodiment;

FIG. 10b shows a side view of the fifth embodiment of FIG. 10a.

It is now referred to FIGS. 1 and 2, where three holding devices 10a, 10b and 10c are shown. The holding devices are mounted on a transportation device (not shown), for example such as those described in the above-mentioned publications. One solar cell wafer 1a is held between the holding devices 10a and 10b, and one solar cell wafer 1b is held between the holding devices 10b and 10c. Hence, the holding devices are provided for holding one end of a wafer on both sides. The loading and unloading of wafers to the holding devices is also described in the above-mentioned publications.

It should be noted the above-mentioned publications describe that the holding devices 10 are fixed to a continuous transportation device, where wafers are continuously received between two holding devices at a first end of the transportation device, while other wafers are continuously released from the transportation device at a second end of the transportation device. During the transportation from the first end to the second end, the wafers are exposed to a process such as submersion into a liquid, electroplating, etc. The first holding device is receiving and holding the front end of the wafer, while the second holding device is receiving and holding the rear end of the wafer, where the terms “front” and “rear” is referring to the transportation direction. Hence, each wafer is held between two holding devices 10.

It is now referred to FIGS. 3 and 4, showing a holding device 10 corresponding to one of the holding devices 10a, 10b, 10c.

The holding device 10 comprises a main body 12 with a substantially wedge-shaped opening 14a and 14b on respective side. The substantially wedge-shaped openings 14a and 14b are adapted to receive an end of a wafer 1, as shown in FIG. 2. Grooves 16 are provided in the lower part of the main body 12 for fastening of the holding device 10 to the transportation device.

The main body 12 comprises a longitudinal opening 18 defining a rotation axis I-I as shown in FIG. 4. The opening 18 is provided in the lower part of the main body 12.

Pressure elements 20 are movably or pivotally connected in grooves provided in the main body 12 to the opening 18, so that they can be pivoted around the rotation axis I-I. In FIG. 4 it is shown that three pairs of pressure elements 20a and 20b are provided in the lower part of the main body 12, where pressure elements 20a are provided on the left side and pressure elements 20b are provided on the right side. The pivotal connection of the pressure elements 20 can for example be provided by a cylindrical pin 18a being inserted through the opening 18 of the main body 12 and corresponding openings in the pressure elements 20 (see FIG. 6). As shown here, the pin 18a is common for both pressure elements 20a and 20b.

The pressure elements 20 comprise floating elements 30 made of a material with a material with positive buoyancy. In the drawings, the floating elements 30 are provided as separate cylindrical floating elements 30 provided in peripherical openings (i.e. provided in a distance away from the pin 18a). The floating elements 30 are hollow cylinders which will be sealed at the ends and therefore they contain air for maximum positive buoyancy. The structures 20a and 20b are preferably made of a material with positive buoyancy relative to the plating liquid (e.g. polypropylene). Both the size of 30 can be altered and/or the distance of 30 to the axis 18 can be changed to reach the desired force from the contacts to the wafer. Alternatively, the floating elements 20 can be provided as a common floating element for all pressure elements 20a and one common floating element for all pressure elements 20b. Alternatively, the floating elements could be incorporated as a part of the pressure element 20 (i.e. the pressure element made of a material with positive buoyancy).

An upwardly protruding electrical contact 40 is provided on each pressure element 20 for contacting the wafer. In FIG. 3 it is seen that when the pressure element 20 is pivoted upwards (in the direction of arrow A), by means of the positive buoyancy caused by the floating element 30 when submerged in a liquid, the upwardly protruding electrical contact 40 will be pressing the wafer towards the upper surface of the substantially wedge-shaped opening 14.

Hence, when the pressure element is in this upper or closed position, the holding device is both holding the wafer and at the same time providing electrical contact to the wafer. When the pressure element is in its lower or open position, the wafer may be received into or released from the holding device.

The upwardly protruding electrical contact 40 is connected to a plate 42 made of a current conducting material. The plate 42 is fixed to the pressure element 20.

A bus connector 44 is provided on top of the main body 12. The bus connector 44 is in electrical contact with the plate 42 and the electrical contact 40 by means of an electric wire 46 provided in channels (not shown) in the main body 12. The electric wire 46 is flexible to allow the movement of the pressure element 20. The bus connector 44 is adapted to be in electrical contact with a bus bar (not shown) connected to a power supply. The bus connector 44 is shaped as a lying U or V, to allow for unobstructed sliding along the bus bar.

In FIGS. 5 and 6 it is shown that the bus connector 44 is connected to the electric contacts 40 of both the right pressure element 20a and the left pressure element 20b. It would of course also be possible to have one common bus connector for all six pressure elements.

It would of course be possible to provide electrical contact by using more than three contacts 40 for each side surface of the wafer and/or to adjust the distance between them.

It would also be possible to replace the three individual electrical contacts 40 for one side of the wafer with one continuous electrical contact.

SECOND EMBODIMENT

In FIG. 7a-7d a second embodiment of the holding device is shown. This holding device is denoted with reference number 110. Many details regarding the second embodiment will not be described in detail here, as they are similar to those described above.

As described in detail with reference to the first embodiment, the device 110 comprises a main body 112 with a substantially wedge-shaped opening 114a and 114b on respective side.

The main body 112 comprises a longitudinal opening 118 provided in the lower part of the main body 112. A pressure element 120 is provided in the opening 118 and allows the pressure element 120 to move upwardly in a substantially linear movement in the direction of arrow B. The pressure element 120 is made of a floating material, i.e. has positive buoyancy in the liquid being used. Alternatively, the pressure element 120 comprises floating elements (not shown) for example incorporated in the body of the pressure element. Ideally, the pressure element 120 incorporates floating elements and the material in 120 is made of a material with a positive buoyancy relative to the liquid being used.

It is now referred to FIG. 7c, where it is shown that the pressure element 120 is substantially T-shaped (an inverted T, i.e. a T turned upside down), comprising a substantially vertical central member 150 and a substantially horizontal cross member 152.

As can be seen in FIGS. 7b and 7c, the floating element 120 comprises an upwardly protruding, substantially T-shaped element 121. The T-shaped element 121 limits both the upwardly and downwardly movement of the pressure element 120 in the opening 118. The substantially T-shaped element 121 corresponds to the substantially vertical central member 150 of the pressure element 120.

Upwardly protruding electrical contacts 140 are provided on the substantially horizontal cross member 152 of the pressure element 120 for contacting the wafer. These are in electrical contact with a bus connector (not shown), as described with reference to the abovementioned embodiment. The substantially horizontal cross member 152 is provided for pressing each wafer towards the upper surface of the substantially wedge-shaped opening 114a, 114b in a direction parallel to the substantially vertical central member 150.

When the pressure element 120 is submerged in liquid, its positive buoyancy causes the pressure element to move upwards in the direction of arrow B, and hence the electrical contacts 140 will contact the wafers provided in the substantially wedge-shaped openings 114a and 114b.

Hence, when the pressure element is in this upper or closed position, the holding device is both holding the wafer and at the same time providing electrical contact to the wafer. When the pressure element is in its lower or open position, the wafer may be received into or released from the holding device.

THIRD EMBODIMENT

In FIG. 8a-8d a third embodiment of the holding device is shown. This holding device is denoted with reference number 210. Many details regarding the third embodiment will not be described in detail here, as they are similar to those described above.

As described in detail with reference to the first embodiment, the device 210 comprises a main body 212 with a substantially wedge-shaped opening 214a and 214b on respective side.

A recess or opening 218 provided in the lower part of the main body 212 (see FIG. 8e). A pressure element 220 is provided in the opening 218. Three substantially cylindrical channels 219 are provided in the main body 212, as indicated with dashed lines in FIG. 8c. Three substantially cylindrical poles 222 are provided in respective channels 219. In their lower end, the poles 222 are fixed to the pressure element 220. In their upper end, the poles 222 are provided with bus connectors or knobs 244 made of an electrical conducting material. The knobs 244 have a substantially spherical shape, and are having a larger diameter than the poles 222. As seen in FIGS. 8b and 8c, the poles 222 are longer than the channels 219.

Consequently, the pressure element 220 together with the poles 222 and knobs 244 are allowed to be moved upwardly and downwardly in a substantially linear movement in the direction of arrow C. The movement is limited by the knobs 244 being larger than the channels 219 and by the pressure element 222 meeting the lower part of the main body 212.

Upwardly protruding electrical contacts 240 are provided on the pressure element 220 for contacting the wafer. These are in electrical contact with the knobs 244. In this embodiment, bus bars 248 comprise pairs of two spaced apart bars, where the distance between each bar allows the pole 222 to pass through between. Moreover, the bus bars 248 are having an inclining end 249.

Also in this embodiment, the pressure element may be considered as being substantially T-shaped, comprising a substantially vertical central member 250 and a substantially horizontal cross member 252 (see FIG. 8d). Here, the substantially vertical central member 250 corresponds to the poles 222. The substantially horizontal cross member 252 corresponds to the pressure element where the contacts 240 are fixed.

Also here, the substantially horizontal cross member 252 is provided for pressing each wafer towards the upper surface of the substantially wedge-shaped opening 214a, 214b in a direction parallel to the substantially vertical central member.

Hence, when the pressure element is in this upper or closed position, the holding device is both holding the wafer and at the same time providing electrical contact to the wafer. When the pressure element is in its lower or open position, the wafer may be received into or released from the holding device. In the third embodiment, it is not buoyancy that provides movement of the pressure element 220. Initially, the pressure element 220 is in its lower position. When approaching the end 249 of the bus bars 248, the poles 222 will pass between the bars, while the knobs 244 will be guided or pressed upwards because of the inclining end 249. Consequently, the poles and the pressure element will be guided upwardly in the direction of arrow C, and the electrical contacts 240 will contact the surface of the wafer. Of course, the bus bars 248 will be located in a suitable position over the liquid.

The pressure element 220, poles 222 and knobs 244 may be provided with a spring mechanism (not shown) to dampen the pressure and movement of the pressure element. Alternatively, the poles 222 could be made of a flexible material, or the bus bars could be provided with a spring mechanism.

The abovementioned detailed description is especially provided to illustrate and to describe preferred embodiments of the invention. However, the description is by no means limiting the invention to the specific embodiments.

FOURTH EMBODIMENT

In FIG. 9 a fourth embodiment of the holding device is shown. This holding device is denoted with reference number 310. Many details regarding the third embodiment will not be described in detail here, as they are similar to those described above.

As described in detail with reference to the first embodiment, the device 310 comprises a main body 312 with a substantially wedge-shaped opening 314a and 314b on respective side.

Two recesses or openings 318 are provided in the lower part of the main body 312. Two substantially cylindrical channels 319 are provided substantially vertically in the main body 312, from the lower part to the upper part. Two, substantially T-shaped pressure elements 320 are provided, each comprising a substantially vertical central member 350 and a substantially horizontal cross member 352. The substantially vertical central member 350 comprises poles 322 provided through the substantially cylindrical channel 219. The substantially horizontal cross member 352 is connected to each pole 322. The tip of each cross member 352 is pointing upwardly, forming an electrical contact 340.

Consequently, the substantially horizontal cross member 252 is provided for pressing each wafer towards the upper surface of the substantially wedge-shaped opening 214a, 214b in a direction parallel to the substantially vertical central member.

In this embodiment, both the substantially horizontal cross member 352 and the substantially vertical central member 350 is electrically conducting, forming the electrical connection to the power supply.

In their upper end, protruding out from each channel 319, the poles 322 are provided with one common magnetic bus connector 344. The magnetic bus connector 344 is provided for being attracted upwardly when the holding device is moving under a magnetic bus 348. The magnetic bus connector 344 and the magnetic bus 348 are also providing electrical contact between the pressure element 320 and the power supply.

Consequently, when the holding device moves under the bus 348, the pressure elements 320 will be moved upwardly in a substantially linear movement. Hence, when the pressure element is in this upper or closed position, the holding device is both holding the wafer and at the same time providing electrical contact to the wafer. When the pressure element is in its lower or open position, the wafer may be received into or released from the holding device.

FIFTH EMBODIMENT

In FIGS. 10a and 10b a fifth embodiment of the holding device is shown. This holding device is denoted with reference number 410. Many details regarding the fifth embodiment will not be described in detail here, as they are similar to those described above.

As described in detail with reference to the first embodiment, the device 410 comprises a main body 412 with a substantially wedge-shaped opening 414a and 414b on respective side.

An opening 418 is provided in the main body 418. The opening 418 is a combination of the openings in the fourth embodiment and the opening of the second embodiment. The opening 418 comprises a longitudinal opening 418a provided in a longitudinal direction of the lower part of the main body, and two openings 418b provided transverse to the longitudinal opening.

In this embodiment, the pressure elements 420 is similar to the pressure elements of the fourth embodiment, and will not be described here in detail. The pressure elements are provided in the transverse openings 418b of the main body. In addition, the pressure element 420 comprises a buoyancy element 422 provided in the longitudinal opening 418a. The buoyancy element 422 is fixed to the substantially vertical central member 450 or pole 422, and is vertically movable within the opening 418a. Hence, when the holding device is submerged in liquid, the buoyancy element 422 will be pressed upwardly, and the pressure device will be pressed towards the wafer. When the holding device rises up from the liquid, the buoyancy element 422 will move downwardly, and the wafer may be released from the holding device.

In this embodiment, both the substantially horizontal cross member 452 and the substantially vertical central member 450 is electrically conducting, forming the electrical connection to the power supply.

Hence, when the pressure element is in this upper or closed position, the holding device is both holding the wafer and at the same time providing electrical contact to the wafer. When the pressure element is in its lower or open position, the wafer may be received into or released from the holding device.

In the embodiments described above, the pressure element is movable in relation to the main body. More specifically, the pressure element is movable between an open position for receiving/releasing the wafer, and a closed position for holding and contacting the wafer. In the closed position, the wafer is held between the main body and the pressure element.

Claims

1. Transporting device for transporting wafers through a liquid, where the transportation device is provided for continuously receiving wafers at a first end and transporting them substantially horizontally to a second end before releasing the wafers, where the transporting device comprises at least two holding devices for holding and electrically contacting each wafer between the at least two contacting devices during the transportation through the liquid, where each holding device comprises:

a main body comprising a substantially wedge-shaped opening for receiving an end of each wafer;

an electrical contact for contacting the end of each wafer, where the electrical contact is connected to a power supply;

a pressure element movably connected to the main body, for pressing the electrical contact towards the end of each wafer.

2. Transportation device according to claim 1, wherein the main body comprises one substantially wedge-shaped opening on each side.

3. Transportation device according to claim 1 or 2, where the electrical contact is provided on the pressure element.

4. Transportation device according to claim 1, where the pressure element is provided for pressing each wafer towards an upper surface of the substantially wedge-shaped opening.

5. Transportation device according to claim 4, where the pressure element is substantially T-shaped, comprising a substantially vertical central member and a substantially horizontal cross member, where the substantially horizontal cross member is provided for pressing each wafer towards the upper surface of the substantially wedge-shaped opening in a direction parallel to the substantially vertical central member.

6. Transportation device according to claim 5, where the substantially vertical central member is provided movable in a channel through the main body.

7. Transportation device according to claim 4, where the pressure element is pivotably connected to the main body by means of a pin inserted in the opening of the main body.

8. Transportation device according to claim 1, where the electrical contact is connected to the power supply by means of a bus connector for connection to a bus bar.

9. Transportation device according to claim 8, where the electrical contact is connected to the bus connector by means of an electrical conductor provided in channels through the main body.

10. Transportation device according to claim 3, where the electrical contact is upwardly protruding.

11. Transportation device according to claim 1, where the pressure element is provided in an opening of the main body.

12. Transportation device according to claim 1, where the pressure element comprises floating elements for providing the movement of the pressure element in relation to the main body due to buoyancy forces.

13. Transportation device according to claim 1, where the pressure element comprises a magnet for providing the movement of the pressure element in relation to the main body due to magnetic forces.

14. Device according to claim 1, where the pressure element is connected to poles movably provided in channels in the main body.

15. Device according to claim 14, where bus connectors having a larger diameter than the poles are connected in the end of the poles, and where the movement of the pressure element is caused by inclining bus bars guiding the bus connectors.

16. Transportation device according to claim 2, where the pressure element is provided for pressing each wafer towards an upper surface of the substantially wedge-shaped opening.

17. Transportation device according to claim 3, where the pressure element is provided for pressing each wafer towards an upper surface of the substantially wedge-shaped opening.