The present disclosure relates to systems and methods for electroplating objects, and more particularly to a system and method for electroplating small spherical balls in a manner that produces a highly uniform metallic coating.
This section provides background information related to the present disclosure which is not necessarily prior art.
When attempting to use metal shell capsules as hydrogen isotope fuel containers for laser induced, inertial confinement experiments, as well as other applications, a number of important coating quality characteristics must be considered. One overall goal in manufacturing metal shell capsules is to be able to produce fully dense, metal electrodeposits onto microsphere mandrels. The electrodeposited coatings should ideally have outstanding surface smoothness and thickness uniformity. The coating surface finish should ideally be as good as the mandrel, and the coating composition and thickness must be controllable within close manufacturing tolerances. Ideally, the process should work equally well for low and high density microspheres, that is, objects that float or sink.
Previous attempts at manufacturing small, spherical, metallic shells for the above-described application have involved barrel plating. Barrel plating is a well-established, metal electrodeposition method for making temporary contact with components. Researchers have also attempted methods to roll spheres on straight wall surfaces during the plating process. Other attempts have involved attaching an electrical lead to the microsphere, as well as rolling spheres in confined tracks (e.g., WO 2006106221 A3).
Barrel plating is not suitable for use with sub-millimeter sized components. Other challenges with barrel plating are the high risk of surface damage and the lack of any effective way to track the uniformity of the coatings formed on individual microspheres. Still further, barrel plating is not practical (or feasible) for small batches where thickness uniformity and surface smoothness are important quality characteristics that need to be achieved.
Straight wall conducting surfaces (cathodes) that are also electroplated similarly suffer from significant drawbacks such as uneven build ups of coatings on the conducting surfaces. Microspheres can stick, and metal ions in the electrolyte used during this process are consumed rapidly, which is especially undesirable when precious metals must be used as the coating material.
Applying a coating to the microspheres by using electrical lead attachments are also undesirable because this method results in asymmetrical coatings and leaves unacceptable scars on the microsphere surface.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
In one aspect the present disclosure relates to an apparatus for electroplating an element. The apparatus may comprise a cathode cage assembly. The cathode cage assembly may include a cage member and at least one electrically conductive wire extending along at least a portion of the cage member. The wire may be arranged to form at least one volume within the cage member for retaining an element within the cage member. The cage member and the wire permit a degree of movement of the element during an electroplating process while retaining the element within the volume.
In another aspect the present disclosure relates to an apparatus for electroplating an element. The apparatus may comprise a cathode cage assembly. The cathode cage assembly may include a tubular cage member and a plurality of lengths of spaced apart, electrically conductive wires extending parallel to one another, and which extend through portions of the tubular cage member to form a plurality of adjacent but separate volumes within the cage member. The separate volumes each retain a respective, separate element therein. The separate volumes also permit a degree of axial movement of the element, relative to the cage member and the electrically conductive wires, during an electroplating process while retaining the elements within their respective said volumes.
In still another aspect the present disclosure relates to a method for forming a cage assembly for use in electroplating spherical mandrels with a uniform metallic coating. The method may comprise providing a cage member formed from an electrically non-conductive material. The method may further include securing a plurality electrically conductive wires to the cage member in a spaced apart configuration, wherein the electrically conductive wires are arranged generally parallel to one another such that the electrically conductive wires and portions of the cage member cooperate to form a plurality of adjacent but separate volumes. The method may further include forming the separate volumes such that each is dimensioned to capture a respective one of the spherical mandrels therein while permitting a degree of movement of the spherical mandrels during an electroplating operation.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
Example embodiments will now be described more fully with reference to the accompanying drawings.
The present disclosure is directed to a cage assembly which is effective in enabling a highly uniform metallic coating to be applied to a spherical object, and more particularly to a microspherical object which may be only a few millimeters in diameters, or even less.
Referring to
In one example the microsphere 18 may be made from a metal, but in other embodiments the microsphere may be made from other materials, for example from plastic or another dielectric material, that has a thin conductive metal layer (e.g., 100 nm thick) that has been flashed onto the plastic. And while a plurality of wires 14 form one preferred implementation, a single wire 14 may be used instead. The use of a single wire 14 will involve inserting and looping the wire, in an undulating fashion, repeatedly through the cage member 12 a plurality of times to form the volumes 16. Accordingly, the internal volumes 16 may be formed by using 1, 2, 3 or even greater numbers of distinct lengths of wire 14, and the presently illustrated embodiment of the cage assembly 10 using three independent wires 14a, 14b and 14c is just one example of how the cage assembly may be constructed. In some applications it may be found that the fewer wires that are used the better. In the example shown in
The cage member 12 may be formed from any non-conductive material (i.e., dielectric material) such as plastic or ceramic, although plastic is particularly desirable for its ease of fabrication and relatively low cost. The cage member 12 may be formed as a single piece component, for example through a conventional injection molding or additive manufacturing techniques, or it may be formed from two or more separate component sections that are secured fixedly together using adhesives or mechanical fastening elements. In this example the cage member 12 is a single piece component that includes a plurality of circumferential ribs 20 and uppermost rib 20a which project perpendicularly from a plurality of axially extending, elongated frame sections 22. A bottom wall 24 closes off the bottom of the cage member 12, and a top section 26 enables ends of the wires 14a-14c to be brought out from the cage member.
Within volume section 12b of the cage member 12, which is above uppermost rib 20a in
During assembly, it has found to be helpful to initially thread the three wires 14a-14c through the holes 28 in the cage member 12, and then before twisting the ends of the wires 14a-14c into the twisted length section 30, to insert the microspheres into each of the volumes 16. Since the wires 14a-14c are loose at this point, they can be manipulated slightly (i.e., slightly spread apart) when inserting each of the microspheres 18. Once the microspheres 18 are each positioned in their respective volumes 16, the upper ends of the wires 14a-14c may be twisted together to form the twisted length section 30. To aid in handling and inserting the microspheres 18 into the volumes 16, a well-known vacuum pick-up system with pick-up pen may be used to handle the microspheres 18 and insert them into their respective volumes 16.
Referring briefly to
An important advantage of the cage member 12 is that the wires 14a-14c have a low surface area relative to the microspheres 18. This minimizes unproductive depletion of metal ions in the electrolyte bath solution 44. Also, the open cage architecture enhances anion diffusion away from the microspheres 18 that is induced by stirring, sonication and flowing agitation methods.
Still another advantage of the cage assembly 10 is that the wires 14a-14c are relatively inexpensive and easily replaced when needed, and there is no need to replace the cage member 12. Still further, the cage assembly 10 works equally well and effectively with microspheres 18 that sink or float. The open structure of the cage assembly 10 allows electrolyte bath solution 44 to recirculate around the microspheres 18 when the electrolyte bath solution is agitated by stirring and/or ultrasonic energy. The ultrasonic vibrations and/or vibration applied directly to the cage member 12 keeps the microspheres 18 in constant motion. Since the microspheres 18 are in constant motion while in contact with the wires 14a-14c, rather than static against the wires, this avoids the possibility of sticking between the wires 14a-14c and the microspheres.
While the foregoing description has been focused around the electroplating of microspheres 18, it will be appreciated that the cage system 10 is not limited to use with only spherical shaped elements. Freestanding, sub-millimeter sized elements having non-spherical shapes, as well as irregular or non-uniform shapes, may be electroplated with equal ease and efficiency using the cage assembly 10. The actual volume defined by the volumes 16 may be selected to provide a slightly greater clearance between non-spherical and/or non-uniform shaped elements and the wires 14a-14c, to ensure that random motions of the elements along the wires will be achieved while sonication is taking place.
The wire(s) 104 may be formed from copper or any other material which has excellent electrical conductivity. The gauge of the wire 104 may also vary depending on the specific application. The threading of the wire 104 need not necessarily start at the very top of the tube 102. It is possible that the threading could begin at some midpoint along the axial length of the tube 102.
While a single tube 102 has been shown in
For the above described cage assembly 100, it should be appreciated that the electrolyte is preferably “pulsed” pumped (e.g., using a diaphragm or peristaltic pump) through the tube 102. This agitation “refreshes” the electrolyte in vicinity of the microsphere (or other form of element being plated) and also induces motion to the microsphere thus avoiding the possibility of sticking to wires 104. The pulsed pumping of the electrolyte also randomizes the effective electric field between microsphere and anode 108, resulting in a more uniform coating thickness. And as noted above, for the cage assembly 10, the electrolyte in preferably submerged in an ultrasonicator.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
This application claims the benefit of U.S. Provisional Application No. 62/522,746, filed on Jun. 21, 2017. The entire disclosure of the above application is incorporated herein by reference.
The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the U.S. Department of Energy and Lawrence Livermore National Security, LLC, for the operation of Lawrence Livermore National Laboratory.
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2006106221 | Oct 2006 | WO |
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Number | Date | Country | |
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20180371635 A1 | Dec 2018 | US |
Number | Date | Country | |
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62522746 | Jun 2017 | US |