APPARATUS FOR WET PROCESSING OF A PLANAR WORKPIECE, DEVICE FOR A CELL OF THE APPARATUS AND METHOD OF OPERATING THE APPARATUS

Abstract

A device for a cell of an apparatus for wet processing of a planar workpiece, comprises a structure comprising first and second walls. The workpiece is movable in a central plane through a space between the first and second walls in a first direction (y). Apertures for introducing pressurised liquid between the first and second walls are on opposite sides of the central plane and facing the central plane. The apertures are distributed in the first direction (y) and in a second direction (x) transverse to the first direction (y). Discharge openings for the liquid to leave the space are on opposite sides, in the second direction (x), along the space in the first direction (y). The first and second walls form barriers to liquid flow from the space in a direction (z) perpendicular to the central plane. Channels through the walls are arranged to conduct liquid to respective one of the apertures.

Claims

1. Device for a cell of an apparatus for wet processing of a planar workpiece, comprising: a structure comprising first and second walls (13a,b), wherein the workpiece is movable in a central plane (4) through a space (3) between the first and second walls (13a,b) in a first direction (y), wherein apertures (27) for introducing pressurised liquid between the first and second walls (13a,b) are provided on opposite sides of the central plane (4) and facing the central plane (4), wherein the apertures (27) are distributed in the first direction (y) and in a second direction (x) transverse to the first direction (y), wherein discharge openings (28a,b) for the liquid to leave the space (3) are defined on opposite sides of the space (3), seen in the second direction (x), along an extent of the space (3) in the first direction (y), and wherein the first and second walls (13a,b) form barriers to liquid flow from the space in a direction (z) perpendicular to the central plane (4), characterised in that channels (23a,b,24a,b) are provided through the walls (13a,b), each channel (23a,b, 24a,b) arranged to conduct liquid to a respective one of the apertures (27).

2. Device according to claim 1, wherein the apertures (27) are defined in surfaces of the first and second walls (13a,b) at ends of the respective channels (23a,b, 24a,b).

3. Device according to claim 1, further comprising first and second liquid distribution devices (2a,b), wherein the first and second walls (13a,b) comprise walls (14a,b) of the first and second liquid distribution devices (2a,b), respectively, and wherein the first and second liquid distribution devices (2a,b) are mounted such that the space (3) extends between the liquid distribution devices (2a,b).

4. Device according to claim 1, wherein at least one liquid distribution space (17a,b) extending in the second direction (x) across inlets of the channels (23a,b, 24a,b) is defined on an opposite side of at least one of the first and second walls (13a,b) to the space (3).

5. Device according to claim 4, wherein the liquid distribution space (17a,b) is delimited by a barrier (16a,b), inclined with respect to the wall (13a,b) such that the liquid distribution space (17a,b) tapers towards an edge of the wall (13a,b).

6. Device according to claim 4, further comprising at least one divergent liquid conduit (20a,b), having an inlet (10a,b) connectable to a liquid supply conduit (11a,b) on one side and widening towards an opposite side that is in liquid communication with the liquid distribution space (17a,b) at multiple locations along a width of the divergent liquid conduit (20a,b).

7. Device according to claim 3, wherein the divergent liquid conduit (20a,b) and the liquid distribution space (17a,b) are defined within a chamber (12a,b) within a housing of one of the first and second liquid distribution devices (2a,b) by a barrier (16a,b) extending within the chamber (12a,b).

8. Device according to claim 1, wherein at least one of the discharge openings (28a,b) is formed by a single gap extending between opposing liquid-impervious parts, along the extent in the first direction (y) of the space (3).

9. Device according to claim 1, further comprising at least one liquid-pervious electrode (5a,b), extending in a plane between the central plane (4) and one of the first and second walls (13a,b).

10. Device according to claim 1, further comprising at least one liquid-pervious shielding structure (6a,b), extending in a plane between the central plane (4) and one of the first and second walls (13a,b).

11. Device according to claim 1, wherein nozzles (25a d) extending to the apertures (27) are provided in the first and second walls.

12. Device according to claim 11, wherein orifices (26,27a d) of the nozzles (25a d) are provided with an elongated shape having a larger dimension in the second direction (x) than in the first direction (y).

13. Device according to claim 1, wherein the apertures (27) are aligned in rows extending at least approximately in the second direction (x).

14. Device according to claim 13, wherein the apertures (27) are uniformly distributed within each row.

15. Device according to claim 14, wherein the apertures (27) of each row are offset in the second direction with respect to those of at least one other row.

16. Device according to claim 15, wherein the apertures (27) are aligned in columns extending at an acute angle (a) to the first direction (y).

17. Device according to claim 1, wherein the first and second walls (13a,b) are provided with apertures (27) at at least one of (i) a surface density of at least 460 apertures (27) per m.sup.2 and (ii) a linear density in the second direction (x) of at least 16 apertures (27) per m.

18. Apparatus for wet processing of a planar workpiece, comprising at least one device (1) according to claim 1.

19. Apparatus according to claim 18, further comprising at least one pump for pumping liquid to the apertures (27).

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. Device according to claim 2, further comprising first and second liquid distribution devices (2a,b), wherein the first and second walls (13a,b) comprise walls (14a,b) of the first and second liquid distribution devices (2a,b), respectively, and wherein the first and second liquid distribution devices (2a,b) are mounted such that the space (3) extends between the liquid distribution devices (2a,b).

25. Device according to claim 5, further comprising at least one divergent liquid conduit (20a,b), having an inlet (10a,b) connectable to a liquid supply conduit (11a,b) on one side and widening towards an opposite side that is in liquid communication with the liquid distribution space (17a,b) at multiple locations along a width of the divergent liquid conduit (20a,b).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0075] The invention will be explained in further detail with reference to the accompanying drawings, in which:

[0076] FIG. 1 is a cross-sectional view of part of a cell for electroplating a planar workpiece;

[0077] FIG. 2 is a detailed schematic cross-sectional view showing parts of the cell and flow directions of an electrolyte circulating in the cell;

[0078] FIG. 3 is a plan view of one of two walls between which a workpiece is movable through the cell; and

[0079] FIG. 4 is a plan cross-sectional view of one of two liquid distribution devices forming part of the cell.

DESCRIPTION OF EMBODIMENTS

[0080] A device 1 for forming part of a cell of an apparatus for wet processing of a planar workpiece comprises first and second liquid distribution devices 2a,b.

[0081] It is convenient to define a first direction y, also referred to herein as a longitudinal direction, and a second direction x, transverse to the longitudinal direction y and also referred to herein as a lateral direction (FIG. 4). In use, the planar workpiece is led through a space 3 (FIG. 1) between the liquid distribution devices 2a,b in the first direction y (FIG. 4). The workpiece extends essentially in a central plane 4 (FIG. 2) midway between the first and second liquid distribution devices 2a,b. In the example, the central plane 4 is a generally horizontal plane.

[0082] In the illustrated example, the device 1 is for forming part of an electroplating cell. Thus, the device 1 further comprises a first and second anode 5a,b and first and second shielding structures 6a,b.

[0083] The shielding structures 6a,b may, for example comprise a lattice made of electrically insulating material, e.g. a polymer material. The shielding structures 6a,b are liquid-pervious. The anodes 5a,b may be made of an electrically conducting, e.g. metal, mesh or other lattice structure. The anodes 5a,b are thus also pervious to liquid.

[0084] Although two anodes 5a,b are shown in the drawings, these anodes 5a,b need not extend over the extent of the space 3 in the first direction y. Instead, there may be a series of anodes in a single plane, one after the other in the first direction y. Furthermore, each anode 5a,b may be sub-divided into mutually electrically insulated segments in the second direction x.

[0085] A conveying device 7 (FIG. 1) is shown only very schematically. The conveying device 7 comprises a clamp 8 for holding the workpiece at one lateral edge thereof. Multiple such conveying devices 7 may be provided to hold the workpiece. A drive 9 is arranged to move the conveying device 7 in the first direction y. The drive 9 may be an endless belt or endless chain, for example. In the electroplating process, the workpiece functions as a cathode. The or each clamp 8 is arranged for electrically contact with the workpiece to establish a voltage difference between the workpiece and the anodes 5a,b.

[0086] In the illustrated embodiment, the workpiece is held at only one edge. In other embodiments, the workpiece may be held at both opposite edges, seen in the second direction x. In particular, the workpiece may extend beyond the space 3 in the second direction x and be driven by wheels or belts contacting the workpiece at the edges of the workpiece.

[0087] Each of the liquid distribution devices 2a,b comprises a housing comprising a liquid inlet 10a,b for connection to a respective liquid supply conduit 11a,b. One or more pumps (not shown) are provided to pump the liquid through the liquid supply conduits 11a,b.

[0088] A chamber 12a,b is defined by the housing. Respective composite walls 13a,b comprise a respective housing wall 14a,b of each housing and a further wall 15a,b placed against the housing wall 14a,b. At least facing surfaces of the walls 13a,b are essentially parallel to the central plane 4, as are the anodes 5a,b and shielding structures 6a,b. The component walls 14,15 of each composite wall 13a,b may be made of different materials. For example, the further walls 15a,b may be made of electrically insulating material. The housing wall 14a,b may be made of mechanically stronger material. In an alternative embodiment, the further walls 15a,b are omitted. Only one of the component walls 14,15 of each composite wall 13a,b need be impervious to liquid, as long as the composite wall 13a,b forms a barrier to liquid flow from the central plane 4 towards the liquid distribution devices 2a,b.

[0089] Each chamber 12a,b is sub-divided in a third direction z (FIGS. 1 and 2), transverse to the first and second directions x,y by an internal wall 16a,b (FIG. 1). Each internal wall 16a,b is inclined with respect to the walls 13a,b between which the space 3 is defined. A liquid distribution space 17a,b is defined between the internal wall 16a,b and the wall 13a,b closest to the space 3. The liquid distribution space 17a,b extends in the first direction y over essentially the entire extent of the wall 13a,b in the first direction y in one embodiment. In another embodiment, multiple adjacent liquid distribution spaces 17a,b may be provided side-by-side in the first direction y, each extending in the second direction x from one lateral edge of the wall 13a,b to the opposite lateral edge.

[0090] The liquid distribution space 17 is closed at one lateral end and has an inlet at the opposite lateral end. The liquid distribution space 17 tapers such that the height of the liquid distribution space 17 decreases towards the closed end.

[0091] There is at least one gap 18a-f (FIGS. 1 and 4) between a free end of the internal wall 16a,b and a chamber side wall 19a,b. The at least one gaps 18a-f together extend along an extent of the chamber 12a,b in the first direction y. Each gap 18a-f provides for liquid communication between the liquid distribution space 17 and a divergent liquid conduit 20a,b defined in the chamber 12a,b. An inlet side of the divergent liquid conduit 20a,b is connected to the liquid inlet 10a,b. An outlet side is situated at the gaps 18a-f. In the illustrated embodiment, flow guides 21a-c (FIG. 3) are provided at the outlet side. The flow guides 21a-c sub-divide the divergent liquid conduit 20a,b into parallel channels, in this example four channels. Side walls 22a,b of the divergent liquid conduit 20 are straight in the illustrated example, but could alternatively be curved.

[0092] Each of the walls 13a, between which the space 3 between the liquid distribution devices 2a,b is located is provided with a plurality of channels 23a,b, 24a,b (FIG. 2) terminating in apertures for introducing liquid into the space 3. In the illustrated embodiment, the channels 23a,b, 24a,b are oriented with their longitudinal axes substantially perpendicular to the central plane 4.

[0093] In the illustrated embodiment, the further walls 15a,b are support walls, e.g. made of plastic. Threaded through-bores are provided in the further walls 15a,b, in which nozzle devices 25a-d (FIG. 2) are inserted. Alternatively, the nozzle devices 25a-d can be pressed into the through-bores. The nozzle devices 25a-d completely fill the through-bores, such that liquid can only pass through the further walls 15a,b through the nozzle devices 25a-d. Thus, a section of each of the channels 23a,b, 24a,b is defined by one of the nozzle devices 25a-d.

[0094] The nozzle devices 25a-b are fan nozzle devices 25a-d, which shape the stream of liquid emerging from each nozzle devices 25a-d. To this end, a constriction forms an orifice 26 (FIG. 3) having an elongated shape with a larger dimension in the second direction x than in the first direction y. The same is the case for an exit aperture 27 through which the liquid enters the space 3. This exit aperture 27 is slit-shaped in the illustrated embodiment.

[0095] Gaps 28a,b are defined between the walls 13a,b at the lateral edges of the walls 13a,b. These gaps 28a,b each extend along essentially the extent of the walls 13a,b in the first direction y.

[0096] The liquid thus flows from the middle outwards in the second direction x, in use. The liquid distribution space 17 and divergent liquid conduit 20 ensure that liquid is introduced into the space 3 at a relatively uniform rate, so that the flow accelerates towards the lateral edges of the workpiece. As a result, a self-centring effect is achieved, keeping the workpiece in the central plane without the need for supports that contact the workpiece. Nevertheless, the shielding structures 6a,b ensure that contact with the anodes 5a,b is prevented under all circumstances.

[0097] An example of the device 1 is configured for workpieces having a thickness of up to 100 μm, e.g. up to 60 μm, up to 50 μm, or even up to 10 μm. Typical dimensions for the height of the gaps 28a,b are in the range of 2-50 mm. Liquid is pumped at such a rate that the velocity at the gaps 28a,b is at least 0.1 m/s, e.g. at least 0.5 m/s. The velocity will generally be below 10 m/s, and may be below 5 m/s.

[0098] The shielding structures 6a,b are spaced apart (in the direction perpendicular to the central plane 4) by at least 5 mm and at most 25 mm, e.g. at most 20 mm or even less than 15 mm. A distance from each anode 5a,b to the central plane 4 is at least 8 mm, e.g. at least 10 mm, and generally at most 15 mm, e.g. at most 12 mm.

[0099] In the illustrated embodiment, the nozzle devices 25a-d are arranged in rows extending essentially in parallel to the second direction x. The mutual spacing between the apertures and thus the nozzle devices 25a-d is equal within each row. In the illustrated embodiment, this spacing is also the same for all the rows. However, the nozzle devices 25a-d of each next row in the first direction y are offset in the second direction x with respect to the nozzle devices 25a-d in the preceding row. The offset is the same for each pair of rows, the spacing between rows in the first direction y also being uniform. As a consequence, the nozzle devices 25a-d can be said to be arranged in columns that are at a slight angle α to the first direction y (FIG. 3). A further consequence is that the number of nozzle devices 25a-d can be ten or eleven. The spacing is such as to achieve a linear density of at least 16 apertures 27 per m in the second direction x. In the illustrated embodiment, the surface density is at least 460 per m.sup.2, e.g. at least 600 per m.sup.2. Thus, the dimension of the walls 13a,b in the first direction y is at most 500 mm, e.g. between 400 and 450 mm. The dimension in the second direction x is at most 700 mm, e.g. between 600 and 650 mm. For these dimensions, there are at least 120 apertures 27 per wall 13a,b.

[0100] The invention is not limited to the embodiments described above, which may be varied within the scope of the accompanying claims. For example, although the apparatus of the example is one having a horizontal conveyance plane (referred to as the central plane 4 herein), the same effects are achievable in an apparatus having a vertical conveyance plane. In such a device, the flow field described herein is achievable by submerging the device 1 relatively far into a liquid bath, such that the liquid emerging from the upper one of the gaps 28a,b does not squirt into free space. In embodiments having a vertical conveyance plane, the dimension in the first direction x can be larger, e.g. up to 1300 mm. The minimum number of nozzle devices 25a-d per unit area, as well as the minimum linear density in the second direction x can be about half the values given above for the embodiment having a horizontal conveyance plane without forgoing the effect of keeping the workpiece in the central plane relatively well.

[0101] In an apparatus comprising multiple devices 1 arranged in series, the spacing between the shielding structures 6a,b may decrease in the first direction y.

[0102] The space accessible to liquid need not be completely empty, as long as it can be penetrated by the liquid. Thus, sections of that space may be filled with a porous structure, e.g. foam. This could, for example, serve as a spacer between the walls 13a,b and the anodes 5a,b and/or between the anodes 5a,b and the shielding structures 6a,b.

LIST OF REFERENCE NUMERALS

[0103] 1—Device [0104] 2a,b—Liquid distribution devices [0105] 3—Space [0106] 4—Central plane [0107] 5a,b—Anodes [0108] 6a,b—Shielding structures [0109] 7—Conveying device [0110] 8—Clamp [0111] 9—Drive [0112] 10a,b—Liquid inlets [0113] 11a,b—Liquid supply conduit [0114] 12a,b—Chamber [0115] 13a,b—First and second composite walls [0116] 14a,b—Housing walls [0117] 15a,b—Further walls [0118] 16a,b—Internal walls [0119] 17a,b—Liquid distribution space [0120] 18a-f—Gaps in chambers [0121] 19a,b—Chamber side walls [0122] 20a,b—Divergent liquid conduit [0123] 21a-c—Flow guides [0124] 22a,b—Divergent conduit side walls [0125] 23a,b—First channels [0126] 24a,b—Second channels [0127] 25a-b—nozzle devices [0128] 26—orifice [0129] 27—exit aperture [0130] 28a,b—Gaps