JP4177902B2 - Apparatus for electrolytically treating a plate-shaped workpiece and method for electrically shielding the edge range of the workpiece during electrolytic treatment - Google Patents

Description

The present invention relates to an apparatus for electrolytically processing a plate-shaped workpiece, and to a method for electrically shielding an edge area of the workpiece. Preferably, the apparatus and the method are arranged in a continuous equipment arrangement in which a workpiece is horizontally or vertically aligned when passing through in the case of electroplating or etching a conductor plate (printed circuit board, etc.) or conductor foil. Used.
In a continuous electroplating equipment arrangement, workpieces of various widths are generally created. The anode in the installation must be dimensioned so that it can be processed without any problems with the widest range of plates and foils. In this situation, if the relatively narrow plate or foil is subjected to galvanic action (electroplating) in the above-mentioned arrangement of the equipment in a direction transverse to the conveying direction of the object to be processed, the electric field lines are concentrated in the edge range. Rather a thicker metal layer is created in the edge range. Usually, a predetermined tolerance for the thickness of the metal layer is set, so that the actual usable range on the metallized plate or foil is small for its full width. In manufacturing a conductor plate or foil, only a small tolerance is allowed for the thickness of the metal layer resulting from the requirements for subsequent processing of the plate or foil. Furthermore, conductor plates are generally associated with expensive materials. Therefore, it is desirable to achieve maximum utilization of raw conductor plates subjected to galvanic action, also referred to as utilization (blank / material piece, Nutzen). A uniform layer thickness is therefore achieved up to the edge range of the conductor plate or conductor foil. A known way to influence the layer thickness in the edge area of the object to be electroplated is in the electrical shielding in this edge area using an electrically non-conductive screen.
DE-P 3937926 C2 describes a device for interrupting the field lines in an electroplating installation, particularly for the treatment of conductor plates. The screen is shown in FIGS. 2 and 3 included therein, which is configured with a plurality of partial screens which are themselves individually adjustable. By rotating the partial screen around the axis, the shielding effect of each individual partial screen is increased and decreased. If the individual screens are sufficiently narrow and therefore there are a sufficient number of these screens, the edge covering can be set optimally.
However, a disadvantage that must be viewed broadly is that residual shielding remains over the area of the conductor plate that should not actually be shielded. Furthermore, the costs for implementing this device structurally are substantial. Therefore, as shown in FIG. 4 in the above publication, a flat screen between the edge range of the workpiece and the anode is practically preferable. However, with this arrangement of screens, an optimal certain contour screening is not possible and the required layer thickness tolerance is not achievable at a relatively large edge area on the blank. In addition, this arrangement has the disadvantage of high technical realization costs.
Electroplating operations require a strong structure. Therefore, from JP-A-62 / 151593, a flat and displaceable screen similar to the known one proved to be a practical result. The screen used here is displaced by a driving device acting in a straight line between the edge range of the workpiece and the anode.
The screen formed flat in this way depends on the coverage of the workpiece by the screen and depending on the distance between the screen and the anode or the surface of the workpiece, the lines of force in the edge range of the workpiece. Reduce congestion. The distance between the anode and the workpiece and the current density of the anode and cathode are also important for the electrolytic treatment. The position of the screen during the electrolysis process constitutes a compromise based on these parameters, so that optimal screening must be determined in complex experiments. The aim is to achieve a large range of use within the allowed tolerances without burning edges at high current densities. In the case of an average current density with a fine conductor plate, the unusable edge has a practical width of about 30 mm. For current densities up to 15 A / dm 2, the unusable edge on this screen already has a width of about 50 mm.
US Pat. No. 3,862,891 discloses an electroconductive frame and an anode, as well as an electrically non-conductive shielding screen for equalizing the density of field lines along the object to be electroplated mounted on an article carrier An electroplating apparatus is described. The shielding screen comprises a number of screen parts fixed to the side wall and screwed with suitable guides to be firmly connected to the device. The screen portions are oriented parallel to each other and parallel to the object to be electroplated and the anode. The screen part partially projects into the space between the object to be electroplated and the anode, where the screen part located near the anode is the screen part located near the object to be electroplated Project even more than. It is stated that with this apparatus a uniform electroplating layer thickness can be achieved in the plane of the electroplating frame.
With this apparatus, the set tolerance of the metal layer thickness is not achieved only in the narrowest possible edge range of the workpiece, and the remaining surface of the workpiece is not uniform for the metal layer thickness at all positions. Since the requirements are met, it is not possible to treat the workpieces of different outer dimensions in an optimum electrolytic manner. Continuous operation / running is particularly desirable to allow a short preparation period.
It is therefore an object of the present invention to avoid the disadvantages of the prior art and in particular to provide an apparatus for the electrolytic treatment of plate-shaped workpieces. The plate or foil can be continuously subjected to electrolytic treatment using this apparatus. The apparatus can be used to change the format of the plate or foil, either quickly, or in some cases manually, to achieve a uniform distribution of the metal layer thickness on the surface of the plate or foil to be processed simultaneously. / Can be adapted to the width. During continuous operation / running, the edge range of the plate or foil where the predetermined layer thickness tolerance cannot be maintained should be as small as possible. However, it is also possible to electrolyze plates or foils in a short processing time, so that as high an electrolysis current as possible is possible in order to enable a high throughput (throughput) of the object to be processed per unit time in the above apparatus. Is required to be used. Even with a large electrolysis current, the thickness of the metal layer on the workpiece should always be kept as uniform as possible up to the edge range.
This problem is solved by the electrolytic treatment apparatus according to claim 1 and by the electrical shielding method according to claim 9.
The apparatus according to the present invention substantially constitutes a continuous equipment arrangement (system) through which an object to be processed passes through a conveyance plane in a substantially horizontal direction of conveyance. In this continuous equipment arrangement, counter electrodes facing substantially parallel to the transfer plane are arranged, and a high current density field (Stromdichtefelder) is shielded between the transfer plane and the counter electrode in the edge range of the workpiece. A screen is arranged for Each of the screens has the shape of at least two flat portions disposed substantially parallel to each other, one portion of the screen being disposed to face the transport plane, and the other portion serving as a counter electrode. It arrange | positions so that it may oppose. The screen is mounted to be displaceable in a direction that extends substantially parallel to the transport plane and substantially transverse to the transport direction.
Furthermore, the continuous equipment arrangement is further required for electrolytic treatment, such as a container for containing the processing liquid, possibly a nozzle, a pump and piping for transferring the liquid to the individual units, through the equipment arrangement described above. A drive unit for transporting the object to be processed, a guide element for holding in the above-described equipment arrangement, a power source, a contact element for the electrode and the object to be processed, and a current supply line.
The method according to the invention is used to electrically shield the edge area during the electrolytic treatment of plate-like workpieces in a continuous installation.
The above apparatus and method are particularly suitable for electrolysis of conductor plates (printed circuit boards, etc.) and conductor foils. The workpiece can be metallized (metallized) by electrolysis or etched. In one case, the workpiece is connected as a cathode and the counter electrode is connected as an anode. In the other case, the object to be treated and the counter electrode are connected with the exchanged polarity.
Preferred embodiments of the invention are described in the dependent claims.
The portion of the screen that directly faces the transport plane is arranged to be retracted from the other portion of the screen by a distance b toward the edge of the workpiece. This enables a very effective shielding of the edge range of the workpiece against the concentration of the field lines. Without such a retraction arrangement of the screen portion (alternate stepping arrangement), it is not possible to achieve an optimal uniform distribution of the metal layer thickness.
In order to adapt the screen arrangement particularly well to the changing formats of the plates or foils to be processed, the flat parts of the screen can be mounted so that they can be shifted (displaced) independently of each other. Depending on the position of the screen part to be predetermined with respect to the position of the anode and the workpiece to be moved, the respective position of the screen part is determined and adjusted during the passage of such a format.
In particular, the distance b can be adjusted by suitable structural elements. Preferably, the distance between the counter electrode and the flat part relative to the transport plane can also be adjusted independently of each other.
For automatic adjustment of the distance b and the distance between the counter electrode, the transport plane and the flat part, for example, a controlled motor drive is provided, by which the screen can be displaced.
In a preferred embodiment, the flat portion has an edge area that can be confronted simultaneously with the workpiece and the counter electrode. The edge area then has openings and / or recesses at the edges.
Since a relatively narrow piece of material can be processed efficiently, the flat part can be made wide when viewed laterally with respect to the conveying direction so that even a narrow workpiece can be reliably shielded in the edge range. It has become.
In general, the counter electrodes, preferably arranged on both sides of the transport plane, have a large number of partial segments when viewed with respect to the transport direction, in order to ensure a single switch-off of the electrodes in the case of a relatively long continuous installation arrangement. It is divided into. This is necessary to avoid current flow to the counter electrode where the workpieces are not facing each other. If the current flow cannot be interrupted by these partial segments, the current density in the edge range increases at the leading edge of the plate or foil, where the metal layer is deposited at a thickness outside the required tolerance range. It will be. Preferably, the screen according to the invention has a length corresponding to the length of the partial segment of the counter electrode when viewed in the transport direction during such segmentation of the counter electrode.
The invention is described in detail below with reference to FIGS.
FIG. 1a: cross section through a double screen and the resulting layer thickness pattern;
Figure 1b: Plan view of the double screen;
Figure 2: Plan view of the edge area of various flat parts of the screen;
Figure 3a: Schematic cross-sectional view of an electroplating installation arrangement without a shielding screen according to the prior art and the resulting layer thickness pattern;
Figures 3b and 3c: Schematic cross-section through the screen arrangement according to the prior art and the resulting layer thickness pattern.
A commonly obtained layer thickness pattern on a plate-like workpiece in the case of an electroplating equipment arrangement without a shielding screen according to the prior art is shown in FIG. 3a. The corresponding pattern is reproduced in FIGS. 3b and 3c when a known screen equipment arrangement with only one screen part is used.
FIG. 3a shows the layer thickness d of the unshielded edge of, for example, a conductor plate after electroplating. A relative layer thickness of d = 1 in the central area of the blank is practically achieved, for example with a layer thickness of 0.03 mm. At the same time, this layer thickness constitutes the desired layer thickness. The position of the object 1 to be processed, for example, the conductor plate with respect to the anode 2 is shown transversely to the transport direction in the cross section. An electric contact portion (not shown) of the conductor plate is located in a range 3 outside the range of the drawing. The conveying and guiding means for the conductor plates in the continuous electroplating equipment arrangement are also not shown in the drawing.
Since the layer thickness pattern on the lower side of the conductor plate is mirror image of the pattern on the upper side, only one anode is shown on one side. The anode / cathode spacing, i.e. the separation of the anode surface from the surface of the workpiece, is practically about 60 mm to about 120 mm for a continuous electroplating installation. The layer thickness pattern 4 schematically sketched here is a relative predetermined layer thickness (desired layer thickness, Soll-Schichtdicke) at a relative distance a = 1 from the side edge (side edge) 5 of the conductor plate. d = 1 is achieved. The field lines are not only due to the field line density extending from the anode surface protruding beyond the conductor plate, but also because the local current density is set in the range at the conductor plate. concentrate. Therefore, an undesirable “layer thickness decrease” 7 is thus formed with a relative thickness of less than d = 1. In this example, the maximum layer thickness is formed directly on the side edge of the conductor plate. In order to avoid the so-called burning phenomenon (a granular metal layer generally formed when the cathode current density is too high), this peak current density must be below the limiting current density at which such burning phenomenon occurs. . A correspondingly low average current density must therefore be adjusted (set) for the electroplating operation.
FIG. 3b schematically shows an electroplating equipment arrangement, which has a flat screen 8 arranged displaceably in the vicinity of the anode 2. However, by using this screen, the basic pattern of the layer thickness does not change. Also in this case, a “layer thickness reduction” occurs, albeit less than without the use of a screen. However, the usable range of the conductor plate material piece is increased by this weak formation of the lowering.
In the case of the equipment arrangement according to FIG. 3c, the usable range is approximately the same size as in the case of the equipment arrangement according to FIG. 3b. Here, the screen 8 is disposed near the surface of the workpiece 1. As the spacing with respect to the conductor plate becomes smaller, the screen edge 9 acts on the conductor plate to concentrate more and more force lines. Therefore, a layer thickness build-up 10 occurs at this position. This rise continues to the side edge 5 of the conductor plate. Even at this distance of the screen from the conductor plate, the usable range of the conductor plate is not larger than in the case of the installation according to FIG. 3b.
On the contrary, the double screen 11 according to the invention is shown in cross section in the upper part of FIG. It comprises a flat part 12 (near the anode) directly facing the counter electrode and a flat part 13 (near the cathode) directly facing the workpiece. Both flat portions are connected to each other by a structural element 14, preferably made of plastic. These structural elements allow a change of their position in the location of the screen portions 12, 13 with respect to each other and to the anode and cathode. This means that the distance 15 between both flat parts as well as the positions of the leading edges 16, 17 of both screen parts are adjustable. Therefore, the projection length 18 (interval b) of the screen portion 12 beyond the portion 13 can be set. The double screen 11 is supported by a bearing 19 so that it can be shifted laterally with respect to the conveying direction.
Of course, other structural solutions for the relative setting of the screen portions of each other can also be selected.
If the screen parameters are set correctly, the double screen 11 almost completely compensates for the “layer thickness drop” 7 and the layer thickness build-up 10 (see the lower figure part in FIG. 1a). Adjustable screen parameters are the distance 15, the protrusion length 18 (spacing b) and the position of the double screen at the spacing between the anode and the workpiece.
Since the spacing of the screen portion 12 near the anode with respect to the anode and the spacing of the screen portion 13 near the cathode with respect to the workpiece is no longer changed for purpose after assembly of the continuous equipment arrangement, the spacing 15 and the projection length 18 (spacing The adjustment of b) must generally be performed manually at the start of operation or operation. A controllable drive device (not shown) produces a movement 20 of the screen part 12 directly opposite the double screen 11 and / or the counter electrode transverse to the conveying direction.
If only a piece of conductor plate blank having a certain width is processed, it is necessary to simply set the screen once manually in order to obtain a predetermined covering 21 in the edge range of the conductor plate.
However, when the width of the conductor plate changes constantly, the conductor plate cover is preferably set by a motor drive device equipped with known control / drive means.
The width of the screen transverse to the conveying direction must be such that at least the narrowest piece of conductive plate material can cover the edge sufficiently.
Basically, the screens 12 and 13 are not firmly connected to each other and can be individually displaced laterally with respect to the conveying direction. This is particularly advantageous when there is a large current density difference from one workpiece to another in the electroplating equipment arrangement. The screen portion 13 close to the cathode can be set to be optimal for avoiding the edge burn phenomenon.
In FIG. 1 b, a further double screen 11 is shown in plan view looking towards the printed circuit board 1. A bearing 19 for holding the screen is arranged between the double screens and at the same time carries the anode. The anodes are segmented and electrically insulated from each other so that they are individually switched on when the workpieces are placed in a continuous equipment arrangement in the transport direction and when the workpieces exit the equipment arrangement Can be switched off. This function is described in the publication DE-P 3939681 A1. Reference is made to this publication. The required length 22 of the double screen depends on the width of the anode segment for the purpose. The conveyance direction of the workpiece is indicated by an arrow 23.
In FIG. 2, an example for a given embodiment of the flat portions 12, 13 is reproduced. By striking the front area of the screen portion, the edge effect is somewhat reduced. The formation of recesses at the leading edges 16, 17 also results in a uniform distribution of the metal layer. Such perforations and / or the addition of recesses are well suited for fine adjustment.
All of the approaches according to the invention lead to practical use of the conductor plate blanks, even in fine conductor technology, reaching at least 12 mm at the conductor plate edge. Further fine adjustment can be achieved by placing a third screen portion between both flat screens 12,13. This mounting of the additional screen part is particularly advantageous and results in a small cost when a single piece of conductor plate blank having a uniform width is processed in a continuous installation arrangement. The motor drive for adapting the position of the screen part to the changing format is omitted in this case.
All of the disclosed features, as well as combinations of the disclosed features, are the subject of the present invention (subject matter) unless expressly indicated to be known.
Reference number list:
1 Object to be processed (for example, printed circuit board)
2 Counter electrode (eg anode)
3 Contact Range 4 Layer Thickness Pattern 5 Conductor Plate Edge 6 Protruding Counter Electrode Range 7 “Layer Thickness Down”
8 Single screen 9 according to the prior art 9 Leading edge 10 of single screen 8 Layer build-up 11 Double screen 12 Screen portion 13 directly facing the counter electrode (close to the anode) 13 Directly facing the workpiece Screen part 14 (close to the cathode) 15 Structural elements 15 for adjusting the screen parts 12, 13 Spacing between the screen parts 12, 13 16 Front edge 17 of the screen part 12 Front edge 18 of the screen part 13 Opposite the workpiece The protruding width of the screen 12 across the screen 13 that faces the counter electrode (interval b)
19 Bearing for holding double screen 20 Screen movement 21 Conductor plate cover 22 Screen length 23 Transport direction

Claims (9)

An apparatus for electrolytically processing a plate-shaped object to be processed in a continuous feed facility arrangement, and the object to be processed can be guided to a transfer plane in a horizontal transfer direction through the continuous feed facility arrangement . A device,
a. A plurality of counter electrodes (2) disposed opposite and parallel to the transport plane; and b. A plurality of screens (11) for shielding a field having a high current density in the edge range of the object to be processed (1) disposed between the transfer plane and the counter electrode.
Have
c. At that time, the plurality of screens are formed in the shape of flat portion arranged parallel to at least two of each other respectively (12,13), one part of the plurality of screens (13) in the transport plane Arranged opposite , the other part (12) is arranged opposite the counter electrode,
d. At that time, the plurality of screens is mounted so as to be displaceable in a direction extending perpendicularly against the parallel and the transport direction (23) against the transport plane (20),
Equipment . The part (13) of the screen (11) disposed directly opposite to the transport plane is disposed so as to recede from the other part (12) by an interval b with respect to the edge of the workpiece (1). The apparatus of claim 1. 3. A device according to claim 1 or 2, characterized in that the flat parts (12, 13) are mounted such that they can be displaced independently of each other. 4. The device according to claim 1, wherein the distance b is adjustable by means of a suitable structural element (14). 5. The device according to claim 1, wherein the distance between the flat part (12, 13) and the counter electrode (2) and the transport plane can be adjusted independently of each other. 6. Device according to claim 1, wherein a controllable motor drive is provided, whereby the screen (11) is displaceable. Said flat portion (12, 13) is, according to, characterized in that a treatment object (1) and the edge region capable facing the counter electrode (2), these edge regions have a depression in the opening and / or edge Item 7. The apparatus according to any one of Items 1 to 6 . The counter electrode (2) is divided into a number of segments as viewed in the transport direction (23), and the screen (11) has a length equal to the length of the segment of the counter electrode (2) in the transport direction. An apparatus according to any one of claims 1 to 7 , characterized in that In the method of electrically shielding the edge region of the plate-shaped workpiece during electric field processing in the continuous feed equipment arrangement where the workpiece is guided to the conveyance plane in the horizontal conveyance direction,
a. A plurality of screens (11) for shielding from the field of high current density in the edge region of the object to be processed (1) are disposed between the transfer plane and the counter electrode (2) arranged to face the transfer plane in parallel. Has been placed,
b. At that time, further the plurality of screens each formed in the shape of at least two flat portions arranged parallel to each other (12, 13), facing one part of the plurality of screens (13) in the transport plane is arranged, the other part (12) is arranged to face the counter electrode,
c. At that time, the plurality of screens is mounted so as to be displaceable in the direction (20) extending perpendicularly to the parallel and the transport direction against the transport plane (23),
Way .

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