GB2538996A

GB2538996A - Selective electropolishing method, appartus and electrolyte

Info

Publication number: GB2538996A
Application number: GB1509563.1A
Authority: GB
Inventors: Benjamin Neill Scott Peter; Syh Chan Kwee
Original assignee: DATUM ALLOYS Pte Ltd
Current assignee: DATUM ALLOYS Pte Ltd
Priority date: 2015-06-02
Filing date: 2015-06-02
Publication date: 2016-12-07
Also published as: WO2016193736A1; GB201509563D0

Abstract

A method, apparatus and electrolyte for selective electropolishing is described. An electrolyte for use in selective electro-polishing is details where an acid, such as phosphoric acid and a sulphuric acid, are used in a water borne formulation with a silica based colloid as a gelling agent to ensure the appropriate viscosity of the electrolyte is used. The metallic workpiece acts as an anode for selective electropolishing an area of a surface of the workpiece, a spacer 18 is positioned on the workpiece 12. An electrolyte medium 12 is applied to a predetermined depth on the electropolishing area and in electrical contact with the anode workpiece 12, and a cover 12 that acts as a cathode positioned on the spacer 18 and in electrical contact with the electrolyte medium 20. A running current is applied with a power source 14 through the cathode cover 16, electrolyte medium 20 and anode workpiece 12 to selectively electropolish the workpiece 12 within the electropolishing area where the electrolyte medium is in contact with the workpiece surface.

Description

SELECTIVE ELECTROPOLISHING METHOD, APPARTUS AND ELECTROLYTE FIELD OF THE INVENTION This invention relates generally to electropolishing of a metallic material, and more particularly to a method, an apparatus and an electrolyte for selective electropolishing of a metallic material.

BACKGROUND OF THE INVENTION

Electropolishing is commonly used in various metal finishing industries to remove defective layers of material from a surface of metallic workpiece. For example in the surface mount technology (SMT) industry, electropolishing is used to deburr and polish the surfaces of metallic sheet stencils. For instance, electropolishing is frequently used to remove the burnt marks, "melted" material caused by the laser beam, and other residue dross around apertures and recesses due to the laser beam entry into the metallic sheet. In the electropolishing process, the removal rate of material is greater at such protrusions than with the recesses along metallic surfaces.

Attempts have been made to remove such undesired laser cut rough surface alterations to make the metallic surface smoother. The most widely used method in the surface mount technology (SMT) industry is the use of a low voltage/high current rectifier on cathodes and the workpiece anode submerged in a heated bath filled with a liquid polishing chemical electrolyte such as mixtures of phosphoric acid and sulphuric acid. The entire laser cut metallic sheet stencil is submerged into the bath and a voltage current is applied across the electrodes to effect the polishing action.

There is concern with polishing the entire workpiece such as the metallic sheet stencil as there is a camera vision feature fiducial marker that is crucial for alignment of the stencil in surface mount technology (SMT) manufacturing process. When the stencil is submerged, the fiducial marker is also polished which may result in removal or degraded fiducial marker that may cause errors in alignment during the manufacturing process. Conventionally, the fiducial marker may be taped over in an attempt to protect the fiducial marker; however, this adds an additional step in the metal finishing process.

There is also concern of the polish chemical electrolyte bath being reused each time for different metallic workpieces. The metallic material debris removed from each workpiece precipitates and remains in the bath which may alter the effectiveness of the electrolyte action of the bath. The electrolyte chemical polish is conventionally heated during the electropolishing process contributing to evaporation into the atmosphere over time requiring the bath to be topped up. Additionally, toxic vapours are emitted during the conventional electropolishing process requiring adequate ventilation. Running the conventional electropolishing process requires time consuming and costly maintenance and upkeep. There is a need for a selective electropolishing method, apparatus and/or electrolyte that addresses or at least alleviates the problems associated with conventional electropolishing processes used in the metal finishing industries.

SUMMARY OF THE INVENTION

An aspect of the invention is a selective electropolishing method comprises providing a workpiece for selective electropolishing an electropolishing area of a surface of the workpiece, the workpiece to act as an anode; positioning a spacer on the surface of the workpiece; applying an electrolyte medium on the electropolishing area of the surface of the workpiece; placing a cover on the spacer and the electrolyte material to cover the electropolishing area on the surface of the workpiece, the cover to act as a cathode; electrically connecting the cathode cover and the anode workpiece to a power source; running an electrical current from the power source through the cathode cover, the electrolyte medium, and the anode workpiece for a predetermined period of time to electropolish the selected electropolishing area of the surface of the workpiece.

An aspect of the invention is a selective electropolishing apparatus comprising a workpiece for selective electropolishing an electropolishing area of a surface of the workpiece, the workpiece to act as an anode; a spacer positioned on the surface of the workpiece; an electrolyte medium in electrical contact with the surface of the workpiece in the electropolishing area of the surface of the workpiece; a cover on the spacer and in electrical contact with the electrolyte medium to cover the electropolishing area of the surface of the workpiece, the cover to act as a cathode; a power source electrically connected to the cathode cover and the anode workpiece, and supply an electrical current from the power source through the cathode cover, the electrolyte medium, and the anode workpiece for a predetermined period of time to electropolish the selected electropolishing area of the surface of the workpiece.

An aspect of the invention is an electropolishing electrolyte for use in selective electropolishing comprising an electrolyte acid compound and a gelling compound. In an embodiment the gelling compound is a waterborne gelling agent. The gelling compound may be a silica based colloid. The gelling compound may be a waterborne silica based colloid. The electrolyte compound comprises a sulphuric acid and phosphoric acid. The electropolishing electrolyte may further comprise water. The electropolishing electrolyte may comprise 25-75% by weight of electrolyte acid compound, 1525% by weight of gelling compound, and/or 10-25% by weight of water compound.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated herein and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. While the invention will be described in connection with certain embodiments, there is no intent to limit the invention to those embodiments described. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the scope of the invention as defined by the appended claims. In the drawings: FIG. 1 shows a simplified schematic block diagram of an apparatus for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention; FIG. 2 shows a simplified schematic block diagram of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation in accordance with an embodiment of the invention; FIG. 3 shows a flow diagram of a selective electropolishing method for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention; FIG. 4 shows a simplified schematic block diagram of an apparatus for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention; FIG. 5 shows a simplified schematic block diagram of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation in accordance with an embodiment of the invention; FIG. 6 shows a simplified schematic block diagram of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation showing the arrangement of the cathode, spacer, and workpiece in accordance with an embodiment of the invention; FIG. 7 shows a simplified schematic block diagram of an arrangement of the cathode, spacer, and workpiece of the area within dashed circle of FIG. 6 in more detail in accordance with an embodiment of the invention; FIG. 8 shows a top plan view of spacer in accordance with an embodiment of the invention; FIG. 9 shows a cross-sectional view of the spacer taken along dashed line A-A of FIG. 8 in accordance with an embodiment of the invention; FIG. 10 shows a perspective view of an apparatus for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention; and FIG. 11-18 show scanning electron microscope (SEM) images of untreated workpiece surfaces in FIG. 11, 13, 15, and 17 before electropolishing, and respective treated surfaces of the workpiece surfaces in FIG. 12, 14, 16, and 18 after electropolishing in an apparatus for selective electropolishing in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

A method, apparatus and electrolyte for selective electropolishing a surface of a metallic workpiece are disclosed comprising a workpiece that acts as an anode for selective electropolishing an electropolishing area of a surface of the workpiece, a spacer positioned on the workpiece with an electrolyte medium applied to a predetermined depth on the electropolishing area and in electrical contact with the anode workpiece, and a cover that acts as a cathode positioned on the spacer and in electrical contact with the electrolyte medium. A running current is applied with a power source through the cathode cover, electrolyte medium and anode workpiece to selectively electropolish the surface of the workpiece within the electropolishing area where the electrolyte medium is in contact with the workpiece surface.

Referring to FIG. 1, a simplified schematic block diagram 10 is shown of an apparatus for selective electropolishing of a surface of a workpiece 12 in accordance with an embodiment of the invention. The apparatus comprises an anode workpiece 12, power source 14, cathode cover 16, a spacer 18, and an electrolyte 20. The electrolyte fills the space defined by the walls of the spacer, the surface of the workpiece 22 and a side wall of the cathode cover. A power source 14 is electrically connected to the anode workpiece 12 which is positively charged and a cathode cover 16 which is negatively charged to complete the electro-chemical circuit. During electropolishing, the cathode cover is in physical contact with a spacer 18. The spacer is in physical contact with a surface of the anode workpiece 12. The spacer acts as an insulator, and contains and holds the electrolyte medium within the electropolishing area. The power source 14 provides a direct current (dc) and applies a voltage such as 12V, 24V, or the like, to ensure a running current of approximately, 1.5 Amp, 2.0, 2.5Amp, or the like, to run a current through a cathode 16, the electrolyte 20 within an electropolishing area 22 on the surface of the workpiece, and the anode workpiece 12. It will be appreciated that the configurations and settings of the power source stated here may vary depending on the required specification, and are not to be considered exhaustive.

FIG. 2 shows a simplified schematic block diagram 30 of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation in accordance with an embodiment of the invention. The horizontal orientation shows the cathode cover 16 is placed on the spacer 18, with the electrolyte 20 applied on the anode workpiece within the electropolishing area 22 defined by the spacer placement on the surface of the workpiece.

FIG. 3 shows a flow diagram 50 of a selective electropolishing method for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention. The metallic workpiece 12 is provided for electropolishing. The spacer 18 is placed in a position 52 on a surface of workpiece to be electropolished. An electrolyte 20 is applied 54 on surface of workpiece within an electropolishing area defined by the spacer 18. The cathode cover is placed 56 on the spacer and electrolyte. A force may be applied onto the cathode cover to discharge electrolyte medium out through an outlet to ensure the electrolyte completely covers the workpiece surfaces within the electropolishing areas. The power source is electrically connected 58 to the cathode cover 16 and anode workpiece 12. The cathode cover 16 is electrically connected to the negative terminal of the power source or ground, and the anode workpiece is connected to the positive terminal of the workpiece. A current is run or applied 60 through cathode cover, electrolyte medium, and anode workpiece to electropolish the surface of the workpiece within the electropolishing area. The current is removed 62 after a predetermined time, such as 25 seconds, 50 seconds, 2 minutes, 4 minutes, or the like. The cover, spacer, and electrolyte are removed 64 workpiece. It will be appreciated that the periods of time stated may vary depending on the required specification, and are not to be considered exhaustive.

In an embodiment, the spacer may be fixed to the surface of the workpiece by an adhesive, tape, or the like. The electrolyte may be applied to a predetermined depth, such as to be level with the height of the spacer, such as for example 1.5mm or the like. The spacer may any suitable thickness to allow the electropolishing action, and a dielectric or insulator, and acid resistant material that does not interfere with the electropolishing process. Such materials of the spacer may be glass, PERSPEX, acrylic resins, or the like. PERSPEX is a registered trademark in some countries of Lucite International Ltd of Southampton, United Kingdom. The spacer may have window dimension of, for example, 240mm x 170mm, and the cover may have dimensions smaller to allow an outlet or discharge of any excess electrolyte medium. It will be appreciated that the dimensions stated here may vary depending on the required specification, and are not to be considered exhaustive.

In an embodiment, the electrolyte medium is a gelling agent acid mixture or blend. The acid mix may comprise different concentrations of acids such as phosphoric acid (H3PO4), sulphuric acid (H2504), and/or the like. Such an acid component may be a metal electrolytic treatment compound such as Electrogleam 55 available from MacDermid, Inc. of Waterbury, Connecticut, United States of America. The gelling agent may be a waterborne gelling agent containing a blend, for example water (H2O) and a gelling agent such as waterborne colloidal silica (Si02) dispersions or the like. The viscous gelling agent, such as a silica based colloid or the like, increases the viscosity of the electrolyte medium acid mix into a paste, gel, sol, emulsion, viscous solution, cream, slurry or the like, to be contained within the spacer during the electropolishing process. The electrolyte medium may contain the compound in various proportions such as for example 25-75% by weight of electrolyte acid compound; 10-25% by weight of water compound; and 15-35% by weight of gelling compound. After electropolishing, the electrolyte medium may be washed off the other components such as the spacer, workpiece surface, cover and the like, with water, or the like.

The viscous gelling agent makes the electrolyte medium viscous, such that it can be handled in a safer manner than in a liquid form of the electrolyte solution. Additional advantages are also realized in transporting the viscous electrolyte medium with increased viscosity.

FIG. 4 shows a simplified schematic block diagram 80 of an apparatus for selective electropolishing of a surface of a workpiece 82 in accordance with an embodiment of the invention. In this embodiment the workpiece 82 is supported by a support 84, workbench, work top or the like. The work top support 84 is preferably an insulator or dielectric and an acid resistant material, such as for example, glass, PERSPEX, and the like. The workpiece has a bore 86, hole, or the like through the workpiece with sides 88 of the bore. Such a workpiece may be a metallic sheet stencil or the like. Although a bore is shown, there may be recesses instead or in addition to the bore 86. The electrolyte medium 20 fills the spaces of the recesses, bores 86, holes and the like, to the support 84. Accordingly the surfaces that are included in the electropolishing area of the workpiece includes the surface of the sides, side wall surfaces 88, or the like of the bores 86, holes, recesses, or the like. FIG. 5 shows a simplified schematic block diagram 90 of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation in accordance with an embodiment of the invention. The horizontal orientation shows the cathode cover 16 is placed on the spacer 18, with the electrolyte 20 applied on the anode workpiece within the electropolishing area 22 including the stencil bores 86 and side walls 88 forming the surface of the electropolishing area defined by the spacer 18 placement on the surface of the workpiece.

FIG. 6 shows a simplified schematic block diagram 100 of an apparatus for selective electropolishing of a surface of workpiece in a horizontal orientation showing the arrangement of the cathode 16, spacer 102, and workpiece 12 in accordance with an embodiment of the invention. The spacer 102 in this embodiment has a rebate 104, in which the cover 16 is placed after the electrolyte is applied in the electropolishing area of the surface of the workpiece within the area defined by the spacer. The rebate 104 of the spacer also may define the depth of electrolyte medium. Dashed circle 106 marks the portions of the spacer, cathode, and anode arrangement that is shown in more detail in FIG. 7 FIG. 7 shows a simplified schematic block diagram 120 of an arrangement of the cathode 12, spacer 102, and workpiece 12 of the area within dashed circle 106 of FIG. 6 in more detail in accordance with an embodiment of the invention. Excess electrolyte medium 122 is shown escaping the space defined between the cover 16, surface of the workpiece, and rebate of the spacer. The space formed between the spacer surface and the cover forms an outlet 124 for the excess electrolyte medium to discharge or escape.

FIG. 8 shows a top plan view 150 of spacer 152 in accordance with an embodiment of the invention. The spacer 152 comprises a spacer rebate 154 forming a spacer window 156 which defines electropolishing area of workpiece. Dashed line A-A is the line along which cross-sectional view is taken in FIG. 9 FIG. 9 shows a cross-sectional view 170 of the spacer 152 taken along dashed line A-A of FIG. 8 in accordance with an embodiment of the invention. The width or thickness 172 of rebate 154 may assist in determining depth of electrolyte medium. The rebate 154 provides side walls that may hold the electrolyte medium to a predetermined thickness on the electropolishing area on the surface of the workspace. The width or thickness of the rebate may be for example 1.5mm, 2.0mm, or the like. Accordingly, the layer of electrolyte medium may also be 1.5mm, 2.0mm or the like. The width or thickness of spacer 174 may be for example 5mm, 6mm or the like. The depth of spacer rebate 176, shown as the horizontal shelf of the spacer on which the perimeter of the cover rests or is in position during electropolishing may be, for example, 1.0mm, 1.5mm or the like. It will be appreciated that the dimensions stated here may vary depending on the required specification, and are not to be considered exhaustive.

FIG. 10 shows a perspective view 200 of an apparatus for selective electropolishing of a surface of a workpiece in accordance with an embodiment of the invention. An anode workpiece 212 is connected to the positive terminal of the power source 214, and the cathode cover 216 is connected to the negative terminal of the power source 214. A spacer 218 is positioned on the surface of the workpiece, defining the electropolishing area on the surface of the workpiece. An electrolyte medium 220 fills the space defined between the anode workpiece 212, spacer 218 and cathode cover 216 and conducts the electrical current running through the cathode cover, electrolyte medium, and the workpiece from the power source. Any excess electrolyte medium 220 is shown protruding as discharged electrolyte medium from space between perimeter of cover 216 and rebate of spacer 218. An outlet 222 formed by a channel formed of space between perimeter of cover and surface of spacer provides the escape for the excess electrolyte medium. The cover has cover ribs 230 to provide the cover with more rigidity. The cover ribs may be the same metallic material as the metallic material of the cover, or a material different to the metallic material of the cover so long as the cover is electrically connected to the power source.

In this embodiment, the spacer 218 is fitted with a spacer contact 240 for anode workpiece to be electrically connected to the positive terminal of the power source, through the spacer. The spacer is a metallic material such as stainless steel, or the like.

FIG. 11-18 show scanning electron microscope (SEM) images of untreated workpiece surfaces in FIG. 11, 13, 15, and 17 before electropolishing, and respective treated surfaces of the workpiece surfaces in FIG. 12, 14, 16, and 18 after electropolishing in an apparatus for selective electropolishing in accordance with an embodiment of the invention. In the untreated workpieces shown in FIG. 11, 13, 15, and 17, undesired surface projections are shown, for example in FIG. 11 the SEM image 250 shows burrs or projections 252, uneven surfaces or burnt mark 254, and the like. FIG. 12, 14, 16, and 18 show electron micrographs of treated surfaces of the workpiece after electropolishing the untreated workpiece shown in FIG. 11, 13, 15 and 17, respectively.

FIG. 12 shows a SEM image 260 of a surface of a workpiece after electropolishing in an apparatus for selective electropolishing in accordance with an embodiment of the invention with an electrolyte having a first concentration at 12 V, for 25 seconds of electropolishing. The first concentration of the electrolyte medium contains 50 ml of the electrolyte component, 65 ml of gelling agent, and 25 ml of water. The SEM image showing 250 the untreated workpiece before electropolishing is shown in FIG. 11. It can be seen in comparing FIG. 11 and FIG. 12 that the first concentration level of electrolyte medium effectively removes burnt marks 254 around the edge of the aperture and material chip that stuck on laser cut wall.

FIG. 14 shows a SEM image 280 of a surface of a workpiece after electropolishing in an apparatus for selective electropolishing with a second, higher concentration of electrolyte concentration than shown in FIG. 12 in accordance with an embodiment of the invention. The second concentration of the electrolyte medium contains 100 ml of, and 25 ml of. The SEM image 270 showing the untreated workpiece before electropolishing is shown in FIG. 13. It can be seen in comparing FIG. 13 and FIG. 14 that the second, higher concentration does have an impact on the aperture wall compared to the first, lower concentration electrolyte medium.

FIG. 16 shows a SEM image 300 of a surface of a workpiece after electropolishing in an apparatus for selective electropolishing with second, higher concentration of electrolyte, at a higher voltage of 24 V from power source for the same amount of time of 25 seconds as the treated workpiece shown in FIG. 12 in accordance with an embodiment of the invention. The SEM image 290 showing the untreated workpiece before electropolishing is shown in FIG. 15. It can be seen in comparing FIG. 15 and FIG. 16 that the second, higher concentration does have an increased polishing action shown as a whiter surface.

FIG. 18 shows a SEM image 320 of a surface of a workpiece after electropolishing in an apparatus for selective electropolishing with the second, higher concentration for a longer or extended period of time, such as 50 seconds, than shown in the treated workpiece shown in FIG. 12 in accordance with an embodiment of the invention. The SEM image 310 showing the untreated workpiece before electropolishing is shown in FIG. 17. It can be seen in comparing FIG. 17 and FIG. 18 that a better result is achieved with increasing the polishing time and higher gel concentration.

The selective electropolishing method and apparatus in accordance with embodiments of the invention have a footprint that is smaller than the conventional electropolishing heater bath system. The selective electropolishing method and apparatus may also be conducted in different orientations, such as horizontal and the like, in contrast to the vertical orientation of the conventional electropolishing heater bath systems. The selective electropolishing method and apparatus requires minimal maintenance when compared with conventional electropolishing heater bath systems. The electrolyte may be used fresh during each electropolishing in the selective electropolishing method and apparatus unlike the reused electrolyte of the conventional systems. The selective electropolishing method may be configured for different areas, such that the electropolishing area may be set for depending on each particular specification, such that only the surfaces of the workpiece that require electropolishing are actually electropolished.

Embodiments of the invention have been described herein. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by the applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

CLAIMS: 1. An electropolishing electrolyte for use in selective electropolishing comprising: an electrolyte acid compound and a gelling compound.
2. The electropolishing electrolyte of claim 1 wherein the gelling compound is a waterborne gelling agent.
3. The electropolishing electrolyte of claim 1 or 2 wherein the gelling compound is a silica based colloid.
4. The electropolishing electrolyte of any one of claims 1 to 3 wherein the gelling compound is waterborne silica based colloid.
5. The electropolishing electrolyte of any one of claims 1 to 4 wherein the electrolyte compound comprises a sulphuric acid and phosphoric acid.
6. The electropolishing electrolyte of any one of claims 1 to 5 further comprising water.
7. The electropolishing electrolyte of any one of claims 1 to 6 comprising 25-75% by weight of electrolyte acid compound.
8. The electropolishing electrolyte of any one of claims 1 to 7 comprising 15-25% by weight of gelling compound.
9. The electropolishing electrolyte of any one of claims 1 to 8 comprising 10-25% by weight of water compound.
10. A selective electropolishing method comprising: providing a workpiece for selective electropolishing an electropolishing area of a surface of the workpiece, the workpiece to act as an anode; positioning a spacer on the surface of the workpiece; applying an electrolyte medium on the electropolishing area of the surface of the workpiece; placing a cover on the spacer and the electrolyte material to cover the electropolishing area on the surface of the workpiece, the cover to act as a cathode; electrically connecting the cathode cover and the anode workpiece to a power source; running an electrical current from the power source through the cathode cover, the electrolyte medium, and the anode workpiece for a predetermined period of time to electropolish the selected electropolishing area of the surface of the workpiece.
11. The selective electropolishing method of claim 10 further comprises fixing the spacer on the surface of the workpiece.
12. The selective electropolishing method of claim of claim 11 further comprises fixing the spacer on the surface of the workpiece with an adhesive.
13. The selective electropolishing method of claim 10 wherein electrically connecting the cathode cover to the negative terminal of the power source and electrically connecting the anode workpiece to the positive terminal of the power source.
14. The selective electropolishing method of claim 10 further comprises removing the electrolyte medium from the surface of the anode workpiece after applying a current.
15. The selective electropolishing method of claim 10 wherein applying the electrolyte medium within the area formed by the spacer, the spacer defining the electropolishing area of the surface of the workpiece.
16. The selective electropolishing method of claim 10 wherein applying the electrolyte medium on the surface of the workpiece to a predetermined depth.
17. The selective electropolishing method of claim 10 wherein applying the electrolyte medium to a depth of the spacer.
18. The selective electropolishing method of claim 10 wherein placing the cover on the spacer forms an outlet for the excess electrolyte medium to escape from a space formed between the perimeter of the cathode cover and the spacer.
19. The selective electropolishing method of claim 10 wherein electrically connecting the anode workpiece with the power source via a connector in the spacer, the connector in electrical contact with the anode workpiece.
20. A selective electropolishing apparatus comprising: a workpiece for selective electropolishing an electropolishing area of a surface of the workpiece, the workpiece to act as an anode; a spacer positioned on the surface of the workpiece; an electrolyte medium in electrical contact with the surface of the workpiece in the electropolishing area of the surface of the workpiece; a cover on the spacer and in electrical contact with the electrolyte medium to cover the electropolishing area of the surface of the workpiece, the cover to act as a cathode; a power source electrically connected to the cathode cover and the anode workpiece, and supply an electrical current from the power source through the cathode cover, the electrolyte medium, and the anode workpiece for a predetermined period of time to electropolish the selected electropolishing area of the surface of the workpiece.
21. The selective electropolishing apparatus of claim 20 further comprising a fastener to fix the spacer onto the surface of the workpiece.
22. The selective electropolishing apparatus of claim 21 wherein the fastener is an adhesive.
23. The selective electropolishing apparatus of claim 20 wherein the cathode cover is electrically connected to the negative terminal of the power source and the anode workpiece is electrically connected to the positive terminal of the power source.
24. The selective electropolishing apparatus of claim 20 wherein the electrolyte medium is within the area formed by the spacer, the spacer defining the electropolishing area of the surface of the workpiece.
25. The selective electropolishing apparatus of claim 20 wherein the electrolyte medium is a predetermined depth on the surface of the workpiece in the electropolishing area.
26. The selective electropolishing apparatus of claim 20 wherein the electrolyte medium has substantially the same depth as the depth of the spacer.
27. The selective electropolishing apparatus of claim 20 further comprising an electrolyte outlet formed between the cover and the spacer for allowing excess electrolyte medium to escape.
28. The selective electropolishing apparatus of claim 27 wherein the outlet is formed space formed between the perimeter of the cathode cover and a surface of the spacer.
29. The selective electropolishing apparatus of claim 20 wherein the spacer further comprises a connector for electrically connecting the anode workpiece with the terminal of the power source.
30. A spacer for use in selective electropolishing in any one of the preceding claims 10-29.
31. A cathode cover for use in selective electropolishing in any one of the preceding claims 10-29.
32. An electropolishing electrolyte for use in selective electropolishing in any one of the preceding claims 10-29.
33. A selective electropolishing apparatus substantially as shown in or described with reference to FIGURES 1-18 of the accompanying drawings.
34. A selective electropolishing method substantially as shown in or described with reference to FIGURES 1-18 of the accompanying drawings.
35. A spacer for use in selective electropolishing substantially as shown in or described with reference to FIGURES 1-18 of the accompanying drawings.
36. A cathode cover for use in selective electropolishing substantially as shown in or described with reference to FIGURES 1-18 of the accompanying drawings.