Electrode and device for electrolytic treatment of a workpiece, assembly for forming a cell of the device, method and computer program

Abstract

An electrode for an apparatus (1) for electrolytically treating a workpiece (3), the apparatus (1) being of a type arranged to transport the workpiece (3) so that the surface to be treated is directed past and toward the surface of the electrode, the electrode being divided into a plurality of segments (23a-e) at at least the surface of the electrode. The segments (23a-e) are arranged adjacent to one another in a first direction (x). Adjacent segments (23a-e) are separated from one another along their respective segment edges (24a-f) to enable adjacent segments (23a-e) to be maintained at different respective voltages. The segment edges (24a-f) extend at least partially in a second direction (y) from a common coordinate value (y0) in the second direction (y) to at least an edge (25, 26) of the conductive portion of the surface of the electrode, the second direction (y) being transverse to the first direction (x) and corresponding to the direction of movement of the workpiece in use. The segment edges (24a-f) between at least one pair of adjacent segments (23a-e) extend along respective paths, the angles of which relative to the electrode surface edge (25, 26) decreasing from the common coordinate value (y0) towards the electrode surface edge (25, 26).

Description

[Technical Field]

[0001] The present invention relates to an electrode for an apparatus for electrolytically treating workpieces, the apparatus being of a type arranged to transport a workpiece having a surface to be treated past and towards the surface of the electrode, the electrode being divided into a plurality of segments at least on this surface of the electrode, the plurality of segments being arranged adjacent to one another in a first direction, adjacent segments being separated from one another along their respective segment edges so as to enable adjacent segments to be maintained at different voltages, the segment edges extending at least partially in the second direction from a common value of a coordinate in the second direction to at least an edge of a conductive portion of the surface of the electrode, the second direction being transverse to the first direction and corresponding to the direction of movement of the workpiece in use.

[0002] The present invention also relates to an assembly for forming a cell of an electrolytic treatment device.

[0003] The present invention also relates to an electrolytic processing apparatus including at least one processing cell.

[0004] The present invention also relates to a method comprising at least one computer-implemented step of designing an electrode of the type described above.

[0005] The invention also relates to a computer program.

[0006] Background technology Yang, L. et al., 'Copper plating uniformity on resistive substrate with segmented anode', ECS Meeting Abstracts, 224th Meeting, Abstract # 2089, 1 November 2013, Retrieved from the Internet:<URL: https: / / iopscience.iop.org / article / 10.1149 / MA2013-02 / 29 / 2089 / pdf> describes a method for improving the uniformity of wafer-scale copper plating on resistive substrates using a segmented anode. In such a plating cell setup, multiple ring-shaped segments are used instead of a single circular anode, and the input current to these segments can be controlled. Specifically, an anode configuration with three concentric segments is disclosed.

[0007] U.S. Patent No. 6,919,010 discloses an anode assembly including an azimuthally asymmetric primary anode and multiple secondary anode segments. The workpiece is positioned above the anode assembly and rotates about an axis substantially aligned with the central axis of the anode assembly. In a typical embodiment, the footprint of the workpiece corresponds (at least roughly) to the periphery of the anode assembly. Initially, only the asymmetric anode is energized to provide current, supplying the majority of the ion current to the central region of the workpiece (near the axis of rotation). The region of the assembly occupied by the segments does not provide any significant current during this initial stage of the plating process, when edge effects are most severe. Thus, at any given time, a relatively large portion of the peripheral edge of the workpiece is not located above the top surface of the anode (or otherwise aligned with any portion of the anode). The plating cell includes a container for holding an electrolyte. A wafer holder holds a wafer having a seed layer disposed thereon. The circuit variably distributes plating current to each of two anodes: an asymmetric primary anode and an asymmetric secondary anode.

[0008] EP 1419290 discloses a horizontal electroplating system for circuit boards, including upper and lower anodes arranged in tandem with one another in the transport direction of the circuit board. The workpiece, in this case a circuit board, is held by at least one clamp, electrically contacted, and transported from one anode to the next. Current is supplied to the circuit board via the contacts and clamps. The anode is divided into individual, electrically isolated anode segments, which are separated transversely across the transport direction. The anode segments, together with a base layer on the circuit board, form partial cells of the electrolyte. Each partial cell is supplied with current from a separate current source, e.g., a respective segment rectifier. The circuit board to be processed constitutes the cathode of the partial cell having the upper layer to be metallized. In one embodiment, the separation lines defining the anode segments extend at an angle α>0 with respect to the transport direction of the workpiece. If the inclination of the separation line is sufficiently large, and therefore the inclination of the segmentation of the anode and the insulator is sufficiently large, then almost all areas of the circuit board to be manufactured will extend above or below the insulating area of ​​the respective anode for a short period of time. In this way, the influence of the insulator on the layer thickness is balanced. In a preferred embodiment, the angle α with respect to the transport direction in the regions of the lateral edges of the circuit board, especially in the regions close to the clamps, is selected to be smaller than the angle with respect to the transport direction in the regions farther away (far from the contacts). This is because the voltage drop in the base layer due to the high currents generated in the regions close to the clamps is significantly larger per unit length than the voltage drop in the regions farther away from the clamps.

[0009] While the current density across the workpiece can be made more uniform by increasing the number of segments, there are limits to this due to the fact that the insulation between the segments also takes up some surface area. Furthermore, the associated increase in the number of rectifiers required to maintain the multiple segments at their respective individual voltage levels increases the complexity and cost of the electroplating system. In practice, the achievable variation in coating thickness on the workpiece is only 13% or less.

[0010] Further improvements can be achieved by influencing the flow of electrolyte. In current systems with segmented anodes, where a shielding device in the form of a plate with openings is provided between the anode and the workpiece, plugs are inserted into predetermined openings. However, determining which openings to insert the plugs into is complicated, and the actual insertion is time-consuming. The plug pattern depends on the distance between the anode and the workpiece surface. Therefore, this pattern must be determined separately for each anode through which the workpiece is transported, and a new pattern must be determined and set if workpieces with different initial thicknesses are to be processed. Even in this case, thickness variation remains below 7%.

[0011] Summary of the Invention It is an object of the present invention to provide an electrode, an assembly, an electrolytic processing device, a method, and a computer program that enable improved uniformity of current density to be obtained over at least a majority of the extent of the workpiece in a first direction.

[0012] The above object is achieved, according to a first aspect, by an electrode according to the invention, characterized in that the segment edges between at least one pair of adjacent segments extend along respective paths, the angles of the paths relative to the electrode surface edge decreasing from a common value of a coordinate towards the electrode surface edge.

[0013] The electrode can be used as an anode in a cell of a galvanic plating apparatus to plate a planar workpiece, for example in the form of a panel or foil. The electrode can also be used as a cathode in an etching apparatus. The example of a galvanic plating apparatus is used herein to explain the operation of the electrode.

[0014] In such devices, the workpiece is transported vertically or horizontally through the electrolyte. The workpiece is transported so that the surface to be treated passes over and faces the surface of the electrode, the two surfaces being substantially parallel. A non-conductive structure, such as a shielding structure, can be provided between the surface to be treated and the electrode surface.

[0015] At the start of the plating process, only a very thin conductive layer, deposited by, for example, vapor deposition or electroless plating, exists on the surface of the workpiece. The workpiece is electrically contacted by the clamps only at one or both edges (when viewed in a first direction, transverse to the direction of movement). The resistance of the thin conductive layer is relatively high compared to the electrolyte. Therefore, the voltage at the surface of this layer drops relatively steeply in the first direction. If the electrode (which functions as the anode in the plating example) were not segmented, a large current density would exist near the clamp. The current density across the electrolyte bath from the workpiece surface to the anode determines the rate at which the layer thickness increases, so non-uniformity in the current density leads to non-uniformity in the thickness of the layer of plating material deposited.

[0016] The proposed electrode is divided into multiple segments, at least on the surface of the electrode facing the surface to be plated. These segments are electrically isolated or loosely coupled to each other, allowing the segments to be held at different voltages by their respective rectifiers. The current flowing from each segment to the workpiece surface can be individually controlled. The segments are positioned adjacent to each other in a first direction, i.e., the direction of voltage drop at the workpiece surface, thereby maintaining a more uniform voltage difference across the electrolyte bath.

[0017] Adjacent segments are separated from one another along their respective segment edges that extend partially in a second direction that is transverse to the first direction and corresponds to the direction of movement of the workpiece in use.

[0018] The segment edges extend from a common value of the coordinate in the second direction to an edge of at least the conductive portion of the electrode surface. The common value of the coordinate can correspond to opposite edges in the second direction. Alternatively, if the path of the segment edges consists of two sections that are mirror images of each other, the common value of the coordinate can correspond to the center of the electrode. The segment edges generally extend to each end point of the edge of the conductive portion of the electrode. The value of the coordinate in the second direction at each end point generally deviates from the average value of the coordinate at these end points by less than 10%, for example less than 5%. In most embodiments, the value of the coordinate in the second direction at each end point is the same. Thus, the edge is substantially straight. This is generally true for electrodes for apparatuses for electrolytically treating workpieces, the apparatus being of a type arranged to transport the workpiece past the surface of the electrode. Otherwise, the workpiece would not be treated evenly across its width (corresponding to the first direction). Furthermore, in this case, multiple electrodes of this type can be arranged in a row in a second direction corresponding to the direction of movement of the workpiece in use, without large, non-uniform gaps between successive electrodes.

[0019] If the segment edges were to extend only in the second direction, meaning that they were straight, the result would be lines on the surface of the workpiece, and the gaps separating the edges of adjacent segments would block the flow of current through the electrolyte bath. Furthermore, there would still be non-uniformities in the current density in the first direction between the coordinates of the segment edges, i.e., within the sections corresponding to the electrode segments.

[0020] The latter effect is countered by the fact that the segment edges between at least one pair of adjacent segments extend along their respective paths, and the angle of the paths relative to the electrode surface edge decreases from a common coordinate toward the electrode surface edge. Because the angle decreases, the path becomes a curved or piecewise linear curve rather than a straight line. At each coordinate in the first direction, the workpiece passes through the two segments for different durations, and the ratio between these durations varies nonlinearly to compensate for the nonlinear voltage drop in the conductive layer on the workpiece surface. As a result, the average current density is relatively uniform in the first direction. This is true at least for the central region away from the edges, because edge effects due to electrolyte flow and workpiece contact can be additional sources of nonuniformity.

[0021] The segment edges between all pairs of adjacent segments generally have the same shape, and both opposing segment edges of each segment can extend along respective paths having different shapes.

[0022] In one embodiment, at least within each half of the electrode when viewed in the first direction, the paths extend in the same orientation in the first direction from a common value of the coordinate to the electrode surface edge.

[0023] That is, within each half of the electrode, at least when viewed in the first direction, all paths are inclined in the same direction. The direction of movement in the first direction along each path of a virtual observer proceeding along the path from the point at which the second coordinate is at the common value to the electrode surface edge has the same sign. The sign is not only the same along the extent of each path, i.e., does not change along the path, but is also the same for all relevant paths (all of the paths or all of the paths within each half). In applications where the workpiece is contacted at both opposing edges, the paths extend in the same direction in the first direction only within each half of the electrode, from the common value of the coordinate to the electrode surface edge. In applications where the workpiece is contacted at only one edge, all paths extend in the same direction in the first direction, from the common value of the coordinate to the electrode surface edge.

[0024] In one embodiment, the path from the common coordinate value to the electrode surface edge is a curve.

[0025] This embodiment achieves a more uniform current density average compared to a piecewise linear curve.

[0026] In one embodiment, at least the conductive portion of the electrode surface comprises two halves when viewed in the second direction, with each section of the segment edge in one half being a mirror image of each section of the segment edge in the other half with respect to a line of symmetry located at a common value of coordinates.

[0027] This allows the path to have a greater slope, which in itself helps to avoid striping effects caused by sections of the workpiece surface passing only or nearly only through the non-conductive separation between the segments.

[0028] In one embodiment, a point on the electrode surface edge along the path of a first one of the segment edges of each segment is at the same coordinate value in a first direction as a point at a common coordinate value on the path of the other segment edge of the segment, or is spaced apart in a first direction from this point.

[0029] If a coordinate in the first direction is labeled x-coordinate and a coordinate in the second direction is labeled y-coordinate, the first edge of a segment extends from point (x1, y0) at the common y-coordinate (y0) to point (x2, y1) at the electrode surface edge. The second edge of the segment extends from point (x3, y0) at the common y-coordinate (y0) to point (x4, y1) at the electrode surface edge. In this embodiment, x3 ≥ x2. As a result, there is no value of the coordinate x in the first direction where the workpiece surface passes under or over the insulating barrier between adjacent segments more than once. Furthermore, each point on the workpiece surface experiences at most two segment voltages, which simplifies the configuration of device cells containing the electrodes.

[0030] In one embodiment, within each half of the electrode when viewed at least in the first direction, the width of the segments, which corresponds to the distance between the edges of the segments at a common value of the coordinate, increases from segment to segment in the first direction.

[0031] This also takes into account the fact that the voltage at the workpiece surface drops off most sharply at the edge where the workpiece is contacted. If the electrode is intended for use in an application where the workpiece is held at both edges by clamps that determine the voltage on the electrode, the above conditions apply within each half of the electrode when viewed in the first direction, with the width being smallest where the two halves meet.

[0032] Such an effect is also achieved in an embodiment in which, within each half of the electrode when viewed in at least a first direction, the angle of the path of a pair of segment edges between a pair of adjacent segments at the surface edge relative to the electrode surface edge increases with each pair in the first direction.

[0033] The segment edge closest in the first direction to the electrode edge with which the workpiece is electrically contacted has a relatively small slope, while the segment edge further away from this electrode edge has a relatively large slope. Again, if the electrode is intended for use in an application in which the workpiece is held at both edges by clamps that determine the voltage on the electrode, the above condition applies within each half of the electrode when viewed in the first direction, with the angle being smallest for the pair nearest where the two halves meet.

[0034] In one embodiment, the electrode comprises a mesh electrode.

[0035] In particular, the electrode surface, and thus the segment surface, can be formed by a mesh. One advantage is that the electrolyte can flow through the electrode. Therefore, the electrolyte between the electrode and the workpiece surface can be replenished relatively uniformly. This can be achieved without the need for a conduit or the like between the electrode and the workpiece. This in itself makes it possible to achieve a relatively uniform average current density.

[0036] In one embodiment, the electrode is at least according to a design that can be obtained by carrying out a method according to the present invention, if not by carrying out a method according to the present invention.

[0037] According to another aspect, an assembly according to the invention for forming a cell of an electrolytic treatment device comprises at least one electrode according to the invention.

[0038] Of course, two such electrodes may be provided in the cell, for example, to simultaneously process both sides of a planar workpiece. The cell further includes at least one device for filling the space between the workpiece surface and the electrode with electrolyte. The at least one device may be configured to circulate the electrolyte so that it exits the space between the workpiece surface and the electrode through a window provided at the edge of the electrode in a first direction.

[0039] One embodiment of the cell further includes at least one shielding device extending in a first direction and a second direction in front of the electrode surface of one of the at least one electrode.

[0040] This embodiment is particularly useful for preventing contact between the electrode and the workpiece when the workpiece is a relatively thin workpiece that is supported only at one or more of its edges. The shielding device can also be used to influence the electric field between the surface of the workpiece to be processed and the electrode surface. The shielding device can be used, in particular, to improve the uniformity of the current density average, for example by compensating for edge effects.

[0041] In one example of such an embodiment, the shielding device includes a plate that is permeable to the liquid and has a plurality of through-flow channels distributed in a first direction and a second direction.

[0042] One advantage is that the electrolyte can flow through the shielding device. Therefore, the electrolyte between the electrode and the workpiece surface can be replenished relatively uniformly without the need for a conduit or other device between the electrode and the workpiece. The distribution and / or size of the flow channels can be locally non-uniform to compensate for other inhomogeneities. By allowing more electrolyte to pass locally, the bath resistance is reduced and the current density is increased, thereby compensating for distortions of the electric field caused by other structures or edge effects. Regular flow can be achieved when the flow channels are uniformly and regularly distributed with a constant pitch according to a grid. By locally interconnecting adjacent flow channels, a local increase in permeability can be achieved. By locally omitting flow channels at specific locations on the grid, a local decrease in permeability can be achieved.

[0043] In a particular form of this embodiment, all of the paths extend in the same direction in a first direction from the common value of the coordinate to the electrode surface edge, and in front of the edge of the electrode surface that the paths approach as they progress from the common value of the coordinate to the electrode surface edge, the integral of the liquid permeable area of ​​the through flow paths in a strip of the plate extending in a second direction along the edge of the plate is smaller than the integral of the liquid permeable area in adjacent parallel strips of the plate of the same width.

[0044] The integral of the liquid permeable area of ​​the through-flow passages in a strip of the plate extending in a second direction along the edge of the electrode surface, where the paths approach as they proceed from the common coordinate to the electrode surface edge, may be less than the average value for all parallel strips of the plate of the same width. If all paths extend in the same direction in the first direction from the common coordinate to the electrode surface edge, the electrode is configured for use with a workpiece electrically contacted at only one edge. The strip at the edge of the shield plate facing the opposite edge of the workpiece is relatively impermeable to liquid. This edge has a window through which electrolyte exits the space between the shield and the workpiece surface. Without this relatively closed strip, a relatively high average current density would be achieved at this edge. This would cause a local increase in the thickness of the layer formed in a plating apparatus including the assembly. In other words, an imaginary strip at the edge of the shield plate furthest away from the edge where the electrode is clamped is relatively impermeable to liquid.

[0045] In one example embodiment of the assembly, the cell further includes at least one shielding device extending in a first direction and a second direction in front of the electrode surface of one of the at least one electrode, and the shielding device includes a plate that is permeable to liquid and has a plurality of through-flow channels distributed in the first direction and the second direction, at least one electrical contact is provided for each segment at a respective position having a coordinate in the first direction, and at the coordinate in the first direction, the integral of the liquid permeable area of ​​the through-flow channels in a strip of the plate extending in the second direction is smaller than the integral of the liquid permeable area in adjacent parallel strips of the same width.

[0046] The strips that allow less electrolyte to pass through compensate for the increase in the average current density that would otherwise build up in the coordinate of the first direction of the electrical contact.

[0047] In one example embodiment of the assembly, the cell further includes at least one shielding device extending in a first direction and a second direction in front of the electrode surface of one of the at least one electrode, and the shielding device includes a plate that is permeable to liquid and has a plurality of through-flow channels distributed in the first direction and the second direction, the plate is secured by at least one fastener that extends across the plate and is positioned at an associated position having a coordinate in the first direction, the fastener having a cross section of a predetermined width on the surface of the plate distal to the electrode, and the integral of the liquid permeable area of ​​the through-flow channels in a section of a strip of the plate having a predetermined width extending in the second direction at the coordinate in the first direction is greater than the integral of the liquid permeable area in adjacent sections of adjacent parallel strips of the same width.

[0048] The fasteners prevent the flow of current because they act as electrical insulating elements even though they are made of a conductive material, an effect that is compensated for by the fact that the remaining part of the strip where the fasteners are located is more permeable to the electrolyte.

[0049] In one example of an embodiment of the assembly, in which the cell further includes at least one shielding device extending in a first direction and a second direction in front of the electrode surface of one of the at least one electrode, and the shielding device includes a plate having a plurality of through-flow passages that are permeable to the liquid and distributed in the first direction and the second direction, in front of the edge of the electrode at which the paths begin to diverge as they proceed from the common coordinate value to the electrode surface edge, the integral of the liquid permeable area in a strip of the plate extending in the second direction along the edge of the plate is greater than the integral of the liquid permeable area in adjacent parallel strips of the plate of the same width.

[0050] In front of the edge of the electrode surface, where the paths approach as they progress from the common value of coordinate to the edge of the electrode surface, the integral of the liquid permeable areas of the through flow paths in a strip of the plate extending in a second direction along the edge of the plate may be less than the average value for all parallel strips of the plate of the same width.

[0051] In front of the electrode edge, where the paths begin to diverge as they proceed from the common coordinate to the electrode surface edge, the integral of the liquid permeable area of ​​the strip of plate extending in the second direction along the edge of the plate may be greater than the average value for all parallel strips of the plate of the same width. At the edge of the plate in front of the electrode edge where the workpiece is electrically contacted, more electrolyte is directed through the plate of the shielding device. This encourages current flow through the surface of the workpiece, as opposed to direct current flow from the electrode to a clamp or similar device that electrically contacts the workpiece.

[0052] In one example embodiment of the assembly, the cell further includes at least one shielding device extending in a first direction and a second direction in front of an electrode surface of one of the at least one electrode, and the shielding device includes a plate, the plate being permeable to the liquid and having a plurality of through-flow channels distributed in the first direction and the second direction, the plate being made of an electrically insulating material.

[0053] This simplifies, among other things, the attachment of the plate. The fasteners for attaching the plate must generally extend at least between the plate and the electrode, away from the edge. The fasteners can be made of a conductive material.

[0054] One embodiment of the assembly further includes at least one additional electrode extending in a second direction along an edge of one of the at least one electrodes and in a third direction transverse to the first and second directions.

[0055] The additional electrode extends in a second direction and transversely to both the first and second directions. This additional electrode may be provided, in particular, at an edge of the segmented electrode facing the edge of the workpiece where the workpiece is electrically contacted, for example, by one or more clamps. When the segmented electrode functions as an anode, this additional electrode is also arranged to function as an anode and is also referred to herein as a clamp anode. A clamp anode is a structure whose dimensions in the third and second directions are, for example, several orders of magnitude (10 or even 100 times) larger than its dimensions in the first direction. In use, a controlled current is supplied to the clamp anode near the edge where the workpiece is contacted by the clamp, for example, to affect metal deposition on the workpiece. Because the clamp may not be completely shielded, some of the current from the segmented anode would otherwise flow through the clamp rather than the workpiece. On the one hand, the clamp anode prevents current from flowing from the segmented anode to the clamp and to the edge strip of the workpiece. On the other hand, the clamp anode compensates for any reduction in metal deposition that would result from current flowing from the segmented anode to the clamp instead of the workpiece. A similar effect is obtained in an embodiment in which the segmented electrode and a further electrode function as cathodes and the workpiece is contacted at its edge to function as an anode.

[0056] In a particular implementation of this embodiment, an electrically insulating shield is provided between the further electrode and the segmented electrode, which may take the form of a surface layer on the surface of the further electrode facing the segmented electrode.

[0057] According to another aspect, an electrolytic treatment device according to the present invention comprises at least one treatment cell, the treatment cell comprising at least one assembly according to the present invention.

[0058] As mentioned above, the electrolytic processing equipment may be for electroplating or etching, i.e., for forming or destroying a conductive layer material on the surface of a workpiece.

[0059] One embodiment of an electrolytic processing apparatus includes a plurality of processing cells and a transport system for transporting workpieces through the cells.

[0060] The conveying system may be a vertical conveying system in which the surface of the workpiece extends substantially vertically, or a horizontal conveying system in which the surface of the workpiece extends substantially horizontally so that the workpiece moves through the cells.

[0061] In one implementation of this embodiment, the transport system includes at least one clamp for releasably holding the planar workpiece at an edge of the planar workpiece while the planar workpiece is transported through the cells.

[0062] In areas away from the edge of the workpiece held by at least one clamp, the workpiece may remain unsupported. This helps prevent wear on the workpiece surface. Processing uniformity is also improved in that there is no support structure between the workpiece and the electrode other than the edge of the workpiece held by at least one clamp. Therefore, even if the conveying system is horizontal, the workpiece can be processed on both sides in one cell. The conveying system can use two or more clamps per workpiece. At least one clamp can be attached to an endless chain or belt. Each clamp can be automatically closed at the first cell and automatically disengaged from the workpiece at the last cell in the series of cells through which the workpiece is conveyed. The conveying system can include clamps for holding the workpiece at both opposing edges in a first direction (i.e., transverse to the direction of movement). In this case, the supply points of the applied current can be mirror images of the line of symmetry of the workpiece.

[0063] In a particular form of this embodiment, at least one of the at least one clamp includes an arm including a conductive portion for electrically contacting the workpiece when pressed against a major surface of the workpiece, thereby enabling the workpiece to function as an electrode.

[0064] Thus, the workpiece is held at a particular potential and transported through the device, and clamps are used so that the workpiece is electrically contacted at the surface to be treated.

[0065] In one particular embodiment, at least one end section of the arm for engaging the workpiece includes an electrically conductive core portion covered by an electrically insulating shield except for a surface section for engaging a major surface of the workpiece.

[0066] This helps to avoid coating or stripping of the arm and facilitates treatment of the workpiece surface when it is held by the clamp by forcing current through a conductive layer on the workpiece surface.

[0067] According to another aspect, the method according to the invention comprises at least one step of designing an electrode according to the invention, the step of designing comprising determining the shape of the path.

[0068] Thus, the electrodes can be adapted to the configuration of the processing cell in which they are to be used. In a multi-cell apparatus, the path shape can be different, for example, between the electrodes for different cells. The path shape can be determined depending on at least one of the number of segments, the extent of the electrode surface in a first direction, the resistivity of the electrolyte, the distance between the workpiece and the electrode surface, the resistivity and thickness of the conductive layer on the workpiece surface, and the extent of the electrode surface in a second direction, among others.

[0069] In one embodiment of the method, determining the shape of the path includes determining coefficients of a polynomial, for example a second-order polynomial, of coordinates in a first direction, where the polynomial represents coordinates in a second direction.

[0070] Thus, in a plan view of the electrode surface, the path from the common value of the coordinate in the second direction to the electrode surface edge is based on at least a polynomial, for example, a section of a parabola. A further step of the design step can include fitting the deviation to a parabola or a higher-order polynomial. The process of determining the coefficients can be an iterative process.

[0071] In one embodiment, the coefficients are obtained by calculating a voltage drop function, where the voltage drop function is a function of coordinate in the first direction and represents the voltage change in the first direction along the surface of the workpiece.

[0072] The voltage drop function may be a second order polynomial function. The coefficients may correspond to coefficients of the voltage drop function scaled by the dimension of the electrode surface in the first direction and divided by the voltage difference between adjacent segments having edges extending along the path whose shape is to be determined.

[0073] One embodiment of the method further includes manufacturing the electrode as designed.

[0074] According to another aspect, a computer program according to the invention comprises instructions for causing a computer to carry out design steps of a method according to the invention when the program is run by a computer.

[0075] The computer program may be embodied in one or more computer-readable non-transitory storage media.

[0076] The present invention will now be described in more detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0077] [Figure 1] 1 is a highly schematic plan view of an electrolytic treatment apparatus; [Figure 2] FIG. 10 is a detailed cross-sectional view of a clamping arm for contacting a workpiece being conveyed through the electrolytic treatment device. [Figure 3] 1 is a schematic plan view of the surface of an anode for a cell of an electrolytic treatment device. FIG. [Figure 4] 4 corresponds to the plan view of FIG. 3, but on the opposite side of the anode. [Figure 5] FIG. 1 is a plan view of a shielding device for placement between an anode and a workpiece. [Figure 6] FIG. 2 is a detailed view of a portion of the shielding device. [Figure 7] 1A-1D illustrate the steps of the method used to obtain the anode. [Figure 8]FIG. 8 illustrates an implementation of one of the steps of FIG. 7. [Figure 9] FIG. 1 illustrates the voltage difference between the segments of the anode and the workpiece, the voltage drop in the electrolyte bath between the workpiece and the anode, and the voltage drop in the conductive layer on the surface of the workpiece facing the anode. [Figure 10] FIG. 10 is a schematic plan view of one half of an anode to show how the segment edge shapes are determined. [Figure 11] FIG. 10 illustrates the first stage in determining a target current density average for a segment. [Figure 12] FIG. 10 is a diagram showing the results of determining the target current density average. [Figure 13] FIG. 10 shows the percentage deviation of current density at a position along the length of a workpiece from the average current density calculated by simulating a cell including an anode of the type shown in FIGS. 3, 4, and 10 and a shielding device such as shown in FIGS. 5 and 6.

[0078] Description of the embodiment The electroplating apparatus 1 includes multiple processing cells 2b-d for plating planar workpieces 3a-f. The planar workpieces 3a-f may be, for example, foils or panels formed primarily from a dielectric material. Surfaces parallel to the plane of the workpieces are referred to herein as major surfaces. It is contemplated that at least one of these major surfaces will be plated by the apparatus 1. This includes plating the sidewalls of any vias through the workpieces 3a-f or the sidewalls of trenches within the workpieces 3a-f.

[0079] Only the electroplating apparatus 1 is described and illustrated herein, and is typically preceded by apparatus for performing pre-treatment steps including ablation, desmearing, ion activation, and electroless deposition to form a conductive precursor layer on the workpieces 3a-f.

[0080] It is convenient to define a first direction x, i.e. a dimension of the workpieces 3a-f, also referred to herein as width. A second direction y, transverse to the first direction x, corresponds to the direction of movement of the workpieces 3a-3f through the apparatus 1.

[0081] The apparatus 1 includes a housing 4 defining a bath of circulated electrolyte. Rollers 5a-c support the workpieces 3a-f up to their entry points into the housing 4, where they are engaged by a transport system 6, shown diagrammatically as including a series of clamps 7 for engaging major surfaces of the workpieces 3a-f at their proximal edges 8a-f. Distal edges 9a-d are located at what are referred to herein as windows of the respective cells 2a-d, through which the electrolyte exits the cells 2a-d. In the illustrated embodiment, the workpieces 3a-f are not held at their distal edges 9a-d. The workpieces 3a-f are not supported by any three-dimensional structure between edges 8 and 9. Nevertheless, the workpieces 3a-f are immersed in the electrolyte. In alternative embodiments, support elements can be provided. The workpieces 3a-f can also be clamped on both sides when viewed in the first direction x.

[0082] The clamps 7 automatically engage the workpiece 3b when the workpieces 3a-f enter the housing 4 and automatically disengage when the workpieces 3a-f exit the housing 4. The clamps 7 are supported on an endless belt 10, which may be a belt with a toothed profile, or a chain, which is driven, for example, by one or more drums 11a, 11b around which the endless belt 10 is arranged and which support it.

[0083] It should be noted that Figure 1 is schematic: in an actual implementation, the clamps 7 extend into the cells 2a-d, so that the workpieces 3a-f have little or no protrusion at their proximal edges 8a-f.

[0084] Clamps 7 include an arm 12 (FIG. 2) on each side of workpiece 3a-f. Arm 12 includes an electrically conductive core portion 13 covered by an electrically insulating shield 14 except for a surface section 15 for engaging a major surface of workpiece 3. Each clamp 7 that engages workpiece 3 forms part of an electrical circuit that includes workpiece 3, which functions as a cathode, and an anode 16.

[0085] In the case of cells 2 for plating both major surfaces of a workpiece 3, the arrangement is mirror symmetrical. The present discussion will focus only on components for plating one major surface of the workpiece 3, i.e., the upward-facing major surface in the illustrated embodiment.

[0086] The anode 16 in this example includes two layers 17, 18 (FIG. 2). In alternative embodiments, there may be one layer or more than two layers. At least the lower layer 18, which is proximal to the workpiece 3, includes a mesh section. The mesh is permeable to the electrolyte. The upper layer 17 may be a mesh layer or, as in the illustrated example, a layer formed from plate sections with openings. This allows the electrolyte to flow through the anode 16 toward the workpiece 3.

[0087] A shielding device is disposed between the anode 16 and the workpiece 3, and includes a shielding plate 19 made of an electrically insulating material and having a through-flow passage. The shielding plate 19 functions to prevent short circuits due to contact between the workpiece 3 and the anode 16. In some embodiments, the shielding plate 19 can be omitted. The shielding plate 19 extends in the first direction x and the second direction y in front of the anode surface facing the workpiece 3. The shielding plate 19 can be substantially coextensive with the anode 16. In the illustrated embodiment, slight deviations exist, as will be described below.

[0088] In the illustrated embodiment, clamp anode 20 ( FIG. 2 ) extends in a second direction y along edge 22 ( FIGS. 3 and 4 ) proximal to clamp 7 and in a third direction z transverse to first direction x and second direction y. Clamp anode 20 is provided with a separately controlled current supply (not shown in detail). Clamp anode 20 is positioned to partially block current flow from anode 16 to clamp 7 or to the area of ​​workpiece 3 at its edge that is contacted by clamp 7. Additionally, clamp anode 20 supplies additional current to workpiece 3, thereby ensuring that metal is deposited on clamp 7 rather than on workpiece 3. This further contributes to the uniformity of the layer formed on workpiece 3. If workpiece 3 is a printed circuit board, clamp anode 20 provides the plated edge area, typically up to 25 mm wide, required for contact in subsequent processing steps.

[0089] In one embodiment, the surface 21 of clamping anode 20 facing anode 16 is coated with an electrically insulating material. This is useful because the current from clamping anode 20 is controlled independently of the current from anode 16, and a potential difference can exist between the two currents.

[0090] The layer 18 of the anode 16, having at least the surface facing the workpiece 3, is divided into a plurality of segments 23a-e. Adjacent segments 23a-e are separated from one another along their respective segment edges 24a-h (FIG. 3). The segment edges 24a-e between adjacent segments 23 form pairs. The pairs can be separated by a gap or an electrically insulating material. The width of the gap or the width of the separating strip of electrically insulating material imposes a limit on the number of segments 23a-e that can be provided, but need not determine the maximum number of segments 23a-e.

[0091] In either case, isolation means that the segments 23a-e are electrically isolated from one another. There is a small coupling due to the fact that the electrolyte between the workpiece 3 and the anode 16 and the conductive initiation layer on the surface of the workpiece 3 are conductive. The approach to isolating the segments 23a-e allows adjacent segments 23a-e to be maintained at different voltages. The coupling is smaller than the range that must be controlled to apply an adjustable current to each individual segment 23a-e. The voltage difference of each segment relative to the clamp 7 can be independently controlled by the associated respective rectifier (not shown). This voltage difference is determined by the anode-to-clamp voltage Uc i where i is the number of the segment 23 counting in the first direction x from the segment 23 a that is proximal to the clamp 7 .

[0092] The segment edges 24a-e extend partially in a second direction y from a common y-coordinate value y0 to a first electrode edge 25 that extends in a first direction x. In the illustrated embodiment, the segment edges 24a-e also extend partially in the opposite direction in the second direction y from the common y-coordinate value y0 to a second electrode edge 26 that also extends in the first direction x. Thus, the first electrode edge 25 and the second electrode edge 26 are opposite edges. A line of symmetry 27 is located at the common y-coordinate value y0. The anode 16 can be considered to include two halves 28, 29 when viewed in the second direction y.

[0093] Segment edges 24a-e extend along respective paths whose angles with respect to first electrode edge 25 decrease from a common y-coordinate value y0 to first electrode edge 25. Their angles with respect to second electrode edge 26 also decrease from a common y-coordinate value y0 to second electrode edge 26.

[0094] The segments of the plurality of segment edges 24a-e in the first half 28 of the first and second halves 29 extend in the same direction in the first direction x from a point at a common y-coordinate value y0 to the first electrode edge 25, i.e., the x-coordinate value increases along the path toward the first electrode edge 25. The segments of the plurality of segment edges 24a-e in the second half 29 extend in the same direction in the first direction x from a point at a common y-coordinate value y0 to the second electrode edge 26, i.e., the x-coordinate value increases along the path toward the second electrode edge 26.

[0095] In the illustrated embodiment, the paths of the segment edges 24a-e are curved. In other embodiments, the paths of the segment edges 24a-e may be piecewise linear curves.

[0096] In the illustrated embodiment, a point on the first electrode edge 25 along the path of a first one of the segment edges 24a-h of each segment 23a-e has an x-coordinate value equal to or smaller than a point on the path of the other segment edge 24a-h of that segment 23a-e at the common value y0. Taking the third segment 23c as an example (FIG. 3), the first segment edge 24d extends from point (x1, y0) to point (x2, y1). The second segment edge 24e extends from point (x3, y0) to point (x4, y1), where x4≧x3. As a result, each point on the surface of the workpiece 3 faces at most two electrode segments 23a-e.

[0097] The width of segments 23a-e, which corresponds to the distance between segment edges 24a-h at a common y-coordinate value y0, increases with each segment in the x-direction when counting segments 23a-e from the proximal electrode edge 22. The progressively wider segments 23a-e reflect the fact that when the workpiece 3 is contacted only at the proximal electrode edge 22, the voltage at the surface of the workpiece 3 changes most sharply in the x-direction at this proximal electrode edge 22.

[0098] The segment edges 24a-e also become progressively more curved in the x-direction. In other words, the angle of the path of a pair of segment edges 24a-h between a pair of adjacent segments 23a-e in the first electrode edge 25 relative to the first electrode edge 25 increases with each pair in the x-direction (the paths of the segment edges 24a-h forming such a pair have substantially the same shape). This also applies mutatis mutandis to the angle relative to the second electrode edge 26.

[0099] The shielding plate 19 is provided with a plurality of substantially regularly distributed through-flow passages, some adjacent passages being interconnected to form a single passage having a larger cross-sectional area, and in certain locations passages being omitted (see Figure 6).

[0100] 4, it can be seen that the anode 16 is provided with electrical contacts 30a-f that extend to the lower layer 18 to contact the segments 23a-e. The electrical contacts 30a-f are provided at respective locations having x-coordinates. The integral of the flow area of ​​a strip of the shielding plate 19 extending in the second direction y at a corresponding x-coordinate is smaller than the integral of the flow area of ​​an adjacent parallel strip of the same width. This width generally approximates the width of the electrical contacts 30a-f. This counteracts the tendency of current to flow directly at the locations of the electrical contacts 30a-f.

[0101] Similarly, the shielding plate 19 is secured by at least one fastener 31 a-g (only a few are shown in FIG. 5 for clarity), which extend transversely across the shielding plate 19 and are positioned at associated locations having respective x-coordinates. The fastener 31 has a cross-section of a predetermined width at the surface of the shielding plate 19 distal to the anode 16. The integral of the cross-sectional area of ​​the flow channels in a section of the strip of the shielding plate 19 having a predetermined width and extending in the second direction y at the x-coordinate is greater than the integral of the cross-sectional area of ​​the flow channels in adjacent sections of adjacent parallel strips of the same width. In other words, to compensate for the fact that the fastener 31 behaves as a non-conductive element despite being made of a conductive material, the permeability is increased in the strip sections on both sides of where the fastener 31 is attached to the shielding plate 19.

[0102] The shielding plate 19 is also configured to compensate for edge effects.

[0103] The proximal shield plate edge 32 (FIG. 5), which is proximal to the clamp 7 in the first direction x in use, has an irregular shape. This is to increase the integral of the liquid permeable area in the strip of plate extending in the second direction y along the proximal shield plate edge 32 relative to the corresponding integral in an adjacent parallel strip of the same width. Otherwise, the current density would decrease along the edge of the workpiece 3. While this decrease is not problematic in principle, local decreases would cause increases in adjacent strips of the workpiece 3. This is avoided by increasing the permeability at the proximal shield plate edge 32. Since the channels are of the same size and regularly distributed (with the same pitch), the irregular proximal shield plate edge 32 results.

[0104] The distal shield plate edge 33 is configured to counteract a rapid decrease in current density, particularly when the workpiece 3 has a smaller extent in the first direction x than the anode 16 and shield plate 19. The integral of the liquid permeable area of ​​the flow channels in a strip of the shield plate 19 extending in the second direction y along the distal shield plate edge 33 is smaller than the integral of the liquid permeable area of ​​the flow channels in an adjacent parallel strip of the same width. This helps to avoid the formation of a rib of plating material along the corresponding distal edge 9 of the workpiece 3.

[0105] In the method for obtaining the anode 16, the separation between adjacent segments 23a-e is ignored, as shown in Figures 9 and 10. Each segment edge 24a-h is a second-order polynomial. When viewed in the first direction x, a point on the first electrode edge 25 of each segment edge 24a-h, the last point of which is at the same coordinate value x as a point at the common value y0 of the next segment edge 24a-h, is obtained. The number of segments 23a-e and the dimensions of the anode 16 are also fixed. Within these constraints, the coefficients of the second-order polynomials defining the segment edges 24a-h and the potential difference Uc relative to the clamp are determined. i It remains to determine i=i, where i denotes the number of the segments 23a-e when counting in the first direction x from the proximal segment 23a.

[0106] The potential difference across the bath at the center of the i-th segment when viewed in the first direction x is Umb i The voltage difference between the clamping position and the corresponding position on the surface layer of the workpiece 3 is Um i and the clamp is assumed to be at the origin, i.e., x=0. Referring to FIG. 9, the following equation:

number

[0107] The dashed graph (FIG. 9) shows the voltage target distribution. Note that Um is simply the average voltage in the segment of the surface layer on the workpiece 3 opposite a particular one of the segments 23a-e. The voltage drop in the surface layer is a second order polynomial.

[0108] In the first step 34 of the design process (FIG. 7), design parameters are obtained. These design parameters include the thickness of the layer of conductive material on the workpiece 3, the dimensions of the workpiece 3 in the first direction x and the second direction y, the resistivity of the electrolyte, the distance between the surface of the workpiece 3 and the surface of the anode 16, and the resistivity of the conductive material on the workpiece 3. A further requirement is the nominal current density average across the area of ​​the anode 16. From this, the target current density average for each segment 23a-e is determined using the following formula: CDA[i]=m·i p +n (3) where i is the segment number, p is a fixed value determined empirically, and the values ​​of m and n are obtained by taking the nominal current density average value for the last segment (e.g., i=5 in the illustrated embodiment) and a specific value for the first segment (i=1) determined by trial and error. This process is illustrated in Figures 11 and 12. Figure 11 shows the result of taking an excessively large value for the current density average in the first segment CDA[1]. Figure 12 shows the result of adjusting this value to an appropriate value. The values ​​of the current density average for all other segments 23a-e are obtained using equation (3).

[0109] In the next step 35, the shape of the path of the segment edges is determined.

[0110] As shown in FIG. 8, this step 35 includes the initialization (step 36) and calculation (step 37) of the target current density average for each segment 23a-e according to equation (3).

[0111] This is followed by a series of repetitions of the steps.

[0112] First (step 38), the current density average is calculated for each segment 23a-e. This involves dividing the first half 28 into narrow strips extending from the proximal electrode edge 22 to the opposite edge in a first direction x, each strip having a relatively small dimension in a second direction y. The voltage drop function and the segment voltage Uc are then calculated. i Using the values ​​of Uc and Uc, the current contribution of each segment 23a-e can be calculated for these narrow strips. The contributions of all narrow strips are then summed to obtain the current for each segment 23a-e, which is then divided by the area of ​​that segment. The resulting value is compared to a target value and the value Uc is adjusted to reduce the deviation. i is adjusted (step 39). This calculation (steps 39, 38) is repeated to bring the current density average for segments 23a-e closer to a target value or until another stopping criterion is met (e.g., a predetermined number of iterations).

[0113] Next (step 40), the segment edges 24a-h are adjusted.

[0114] 10 shows the first half 28 of the anode 16. The dashed lines correspond to the paths that points on the workpiece 3 will follow as the workpiece 3 moves in the second direction y. In an electroplating process, the amount of metal deposited is proportional to the charge Q. The charge Q is calculated by multiplying the current I by the time t: Q=I·t (3) is defined by

[0115] The speed v of the workpiece 3 is constant: v=L / t (4) where L is the dimension of the first half 28 of the anode 16 in the second direction y. At each position in the first direction x, the time t is the same, and therefore the charge is the product of the current I and the length L for each point on the workpiece 3 that moves past only one segment 23a-e.

[0116] To achieve equal metal deposition for each position x[i] in the first direction x, the collected charge Q must be the same. This imposes the following constraint: L S5,x[i] I S5,x[i] +L S4,x[i] I S4,x[i] =Q[i]·v, L S5,x[i+1] I S5,x[i+1] +L S4,x[i+1] I S4,x[i+1] =Q[i+1]·v, L S5,x[i+2] I S5,x[i+2] +L S4,x[i+2] I S4,x[i+2] =Q[i+2] v where v and Q are constants.

[0117] The anode segments 23a-e are divided into narrow strips of equal size extending in the y-direction. Each strip extends across two adjacent segments 23a-e. Because each segment 23a-e is at a different voltage, the local current input to the workpiece 3 is also different. The currents along each strip sum together, reflecting that the workpiece 3 has passed in front of the entire anode 16.

[0118] The conductive layer on the workpiece 3 is modeled as a one-dimensional chain of resistors, each with a length in the x-direction corresponding to the distance from one strip to the next. This makes it possible to model the currents input to the nodes of the resistor chain. This results in voltage drops that allow the calculation of a new voltage drop function. This function is a second-order polynomial, as described above. The coefficients of the polynomial determine the shape of the segment edges 24a-h, which are corresponding second-order polynomials. The method then calculates the segment voltage Uc together with the new shape of the segment edges 24a-h obtained in the second step 40. i Return to the calculation.

[0119] The iterations are repeated until a stopping criterion is met (e.g., a fixed number of iterations, a certain maximum deviation of the current density average from the target value, etc.) In one particular embodiment, the stopping criterion is that the current contributions of each of the strips defined in step 40 of adjusting the segment edges 24a-h are equal (or differ by less than a predetermined maximum allowable deviation).

[0120] In an optional further step 41 (FIG. 7), the current density is calculated by simulation over the surface of the workpiece 3. Then (optional step 42), the permeability of the shielding plate 19 is adjusted locally so that the deviation of the current density from the average value is reduced. This takes into account the separations between adjacent segments 23a-e, which are ignored in the calculation of the shape of the segment edges 24a-h. The two steps 41, 42 are carried out iteratively to arrive at an optimal aperture distribution for the shielding plate 19.

[0121] Finally (step 43), the anode 16 is manufactured as designed.

[0122] Simulations of an anode 16 designed with such a process show that the deviation from the average current density remains within 5% over the extent of the workpiece 3 in the first direction x, except for small strips at the edges 8, 9 (Figure 13).

[0123] The invention is not limited to the above-described embodiments but can be modified within the scope of the appended claims. An improved current density uniformity can be achieved, for example, even without the above-described shielding plate 19. [Explanation of symbols]

[0124] 1 device Cells 2a-d 3a~f Workpiece 4. Cabinet 5a~c Roller 6. Transport System 7 Clamp 8a-f Proximal workpiece edge 9a-d Distal workpiece edge 10 Belt 11a,b drums 12 Arm 13 Core part 14 Core shielding 15 Surface division of core part 16 anodes 17 Upper layer 18 Lower layer 19 Shielding Plate 20 Clamp Anode 21 Clamp anode surface 22 Proximal electrode edge Segments 23a~e 24a~h Segment edge 25 first electrode edge 26 Second electrode edge 27 Line of symmetry 28 First Half 29 Second Half 30a~f Electrical Contacts 31a~g Fasteners 32 Proximal shielding plate edge 33 Distal shielding plate edge 34 Steps (Obtaining Design Parameters) 35 steps (Determine the route shape) 36 Steps (Initialize) 37 steps (calculate the target current density average for each segment) 38 steps (determine the actual average current density for each segment) 39 steps (adjust segment voltage) 40 steps (determine new segment edge shape) 41 Steps (Run the simulation) 42 Steps (Optimizing the Shielding Plate) 43 Steps (Manufacturing the anode as designed)

Claims

1. An electrode for a device (1) for electrolytically treating a workpiece (3), comprising: the device (1) is of a type arranged to transport the workpiece (3) so that the surface to be treated passes vertically or horizontally past the surface of the electrode through the electrolyte and is directed towards the surface of the electrode, the electrode is divided into a plurality of segments (23a-e) at least on the surface of the electrode that is directed towards the surface to be treated, The plurality of segments (23a-e) are arranged adjacent to each other in a first direction (x), adjacent segments (23a-e) are separated from one another along respective segment edges (24a-f) to allow adjacent segments (23a-e) to be maintained at different respective voltages; The segment edges (24a-f) have a common value of coordinate in the second direction (y) (y ０ ) at least partially in a second direction (y) to the electrode surface edges (25, 26) of the conductive portions of the surfaces of the electrodes, the second direction (y) is a direction transverse to the first direction (x) and corresponds to a direction of movement of the workpiece; the width of the segments (23a-e), which corresponds to the distance between the edges (24a-h) of the segments (23a-e) at the common value (y 0 ) of the coordinate, increases for each segment (23a-e), such that the segments (23a-e) become progressively wider with increasing distance from the electrode edge (22) in the first direction (x); The segment edges (24a-f) between at least one pair of adjacent segments (23a-e) extend along respective paths, and the angles of the paths relative to the electrode surface edges (25, 26) are determined by the common value (y ０ ) towards the electrode surface edges (25, 26). An electrode characterized by:

2. At least within each half of the electrode when viewed in the first direction (x), the path is ０ ) and gradually move away from the electrode surface edges (25, 26), Within each half of the electrode, at least when viewed in the first direction (x), all paths are inclined in a direction opposite to the electrode edge (22). The electrode of claim 1.

3. The common value of the coordinate (y ０ 3. The electrode according to claim 1, wherein the path from the electrode surface edge (25, 26) to the electrode surface edge (25, 26) is curved.

4. at least the conductive portion of the surface comprises two halves (28, 29) when viewed in the second direction (y), Each section of the segment edges (24a-f) in one half (28, 29) has the common value of the coordinate (y ０ ) and are mirror images of the respective sections of the segment edges (24a-f) in the other half (28, 29) with respect to a line of symmetry (27) located in the other half (29).

4. An electrode according to any one of claims 1 to 3.

5. A point on the path of a first one of the segment edges (24a-f) of each segment (23a-e) at the electrode surface edge (25, 26) is The common value (y ０ ) at the same coordinate value in the first direction (x) as a point in the 5. An electrode according to any one of claims 1 to 4.

6. 6. The electrode according to claim 1, wherein the angle of the path of a pair of segment edges (24a-f) between a pair of adjacent segments (23a-e) at the electrode surface edge (25, 26) relative to the electrode surface edge (25, 26) increases for each pair with the distance from the electrode edge (22) in the first direction (x).

7. When viewed in a plan view of the electrode surface, the common value (y ０ 7. The electrode according to claim 1, wherein each path from the electrode surface edge (25, 26) to the electrode surface edge (25, 26) is based on at least a polynomial.

8. An assembly for forming a cell (2a-e) of an electrolytic treatment device (1), comprising at least one electrode (16) according to any one of claims 1 to 7.

9. The assembly of claim 8, further comprising at least one shielding device extending in the first direction (x) and the second direction (y) in front of an electrode surface of one of the at least one electrodes (16).

10. 10. The assembly according to claim 9, wherein the shielding device comprises a plate (19) permeable to the liquid and provided with a plurality of through-flow channels distributed in the first direction (x) and the second direction (y).

11. Electrolytic treatment apparatus comprising at least one treatment cell (2a-e), The processing cell (2a-e) comprises at least one assembly according to any one of claims 8 to 10. Electrolytic treatment equipment.

12. A method comprising at least one computer-implemented step (34-42) of designing an electrode (16) according to any one of claims 1 to 7, comprising: The designing step (34-42) includes a step of determining a shape of a path. method.

13. Determining the shape of the path includes determining (35) the coefficients of each of a polynomial representing a coordinate in a first direction (x), the polynomial representing a coordinate in a second direction (y); When viewed in a plan view of the electrode surface, the common value of the coordinate in the second direction (y ０ ) corresponds to a polynomial with a respective set of coefficients, 13. The method of claim 12.

14. The coefficients are obtained by calculating a voltage drop function, the voltage drop function is a function of the coordinate in the first direction (x) and represents a voltage change in the first direction (x) along the surface of the workpiece (3); 14. The method of claim 13.

15. A computer program comprising instructions for causing a computer to carry out the designing steps (34-42) of the method according to any one of claims 12 to 14 when the computer program is executed by the computer.

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