Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Applying current to substrate without mechanical contact
Reexamination Certificate
1999-04-12
2001-02-20
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Applying current to substrate without mechanical contact
C205S096000, C205S148000, C204S259000, C204S261000, C204S273000, C204S280000, C204S284000, C204S287000, C204S22400M
Reexamination Certificate
active
06190530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to mechanisms for electrolytic plating and, more particularly, to an anode container, electroplating system, method and object so plated.
2. Related Art
Electrolytic plating system anode containers often consist of an open mesh type structure or basket that contains anode material, sometimes in the form of spheres, that provide electrical contact between anode material and flow of plating solution through the array of anode material. See, for example, U.S. Pat. Nos. 4,059,493 and 4,569,744 to Rice and Walker, respectively. During the electroplating process, anode materials are consumed over time. These baskets commonly have a limitation, that as the anode material dissolvesand the remaining anode material descends toward the bottom of the basket, a bridge or arch will form, preventing the material from descending further in the basket. When a basket having parallel faces is loaded with a particulate medium, such as spheres, an outward pressure is applied to the faces of the anode container and the container faces deform outwardly. Unfortunately, the anode material does not pass the point of maximum deformation, hence, creating a self-supporting bridge or arch area. If there are holes, braces, or supports in the basket, the chance of a bridge or arch is increased. When a bridge or arch is created, the anode material must be removed or repositioned to disassemble the bridge, hence, slowing the overall processes.
If the bridge or arch is not removed, variations in plating thickness can occur. Since the plating ions take the path of least resistance, i.e., the shortest distance, two mechanisms occur to alter the plating deposit. First, the anode material at or below the bridge or arch in the anode container can be depleted reducing available ions with no replacement material passing the bridge or arch. Secondly, the electrical circuit can be disturbed to the lower portion of the anode container, reducing current flow through the anode material below the bridge or arch. Both of these situations reduce the plating in the same region of the plating cell or object(s) being plated. Since most plating systems are time and current controlled, the plating above the bridge or arch in the anode container is increased to compensate for the reduced plating below the bridge or arch, increasing the overall variability of the plating deposited on the object(s).
Previous anode baskets have used expanded mesh members to provide plating solution flow and ion transport. Sometimes, a sheet of metal, such as titanium, is slit and expanded to create the basket by plastic deformation. Unfortunately, the deformation of the slit sheet of metal creates out-of-plane areas in the side of the basket which catch on the anode material. Where the baskets are created by slitting plastic sheets, the baskets are not as strong. See, for example, U.S. Pat. No. 5,340,456 to Mehler.
One way of promoting anode material motion has been to apply a shock or vibration to the anode basket. See, for example, U.S. Pat. No. 3,862,745 to Chiz and U.K. Patent No. 315,481 to Collingridge. Where the baskets are mesh or contain welded joints, the vibration mechanisms can deform the basket and/or break welded joints within the basket. In the case where vibration is applied to the anode material above a bridge or arch, these additional loads are transmitted by the bridge or arch to the face of the anode container, further deforming the container and breaking weld joints.
In view of the foregoing, there is a need in the art for an electroplating system having a strong anode-receiving container that prevents anode bridging and arching.
SUMMARY OF THE INVENTION
In a first general aspect of the invention is provided an electroplating system comprising: a solution tank filled with electroplating solution; an anode-receiving container having an interior cross-sectional area, at or near a lower end thereof, that is larger than an interior cross-sectional area of an upper end thereof, the anode-receiving container containing anode material and being within the solution tank; and a power supply electrically connected to an object to be plated and the anode-receiving container.
In a second general aspect of the invention is provided an anode-receiving container comprising an interior cross-sectional area, at or near a lower end thereof, that is larger than an interior cross-sectional area of an upper end thereof.
In a third general aspect of the invention is provided an anode container comprising: a body having a plurality of sides and an upper and lower end, wherein the lower end has a larger cross-sectional interior area than the upper end.
In a fourth general aspect of the invention is provided an electroplating process comprising the steps of: supporting an object to be plated in a tank filled with electroplating solution; supporting plating material in the electroplating solution in a container having an interior cross-sectional area, at or near a lower end thereof, that is larger than an interior cross-sectional area of an upper end thereof; and supplying an electric current through the object to be plated, the electroplating solution and the container including the plating material, whereby plating material is plated onto the object. In a fifth aspect of the invention an object plated by the above process is provided.
The anode container, electroplating system, and method in accordance with the invention allow the anode material to move downward into a physically larger region, reducing the chance of an arch or bridge from forming. Further, since all structures deform some amount when a force is applied, a container having an interior cross-sectional area, at or near a lower end thereof, that is larger than an interior cross-sectional area of an upper end thereof, can be formed to exceed deformations that the container may experience and therefore insure that the anode material moves into an expanding region. The plated object in accordance with the present invention therefore is more likely to have uniform plating.
The invention may also include a plurality of punched in apertures in the container wall(s). The punched apertures provide a number of advantages. First, they allow for fluid flow without creating areas which can catch on the anode material and thus prevent downward movement of anode material. Second, the punched apertures allow the container to be made of a fewer sheets of material to reduce the number of welds necessary. Accordingly, the invention may also include an apparatus to vibrate the container to further aid in the prevention of bridging with less worry about breaking mesh or welds. Last, by tailoring the punch size and spacing, various percentages of open areas can be developed such that ribs of solid material can be left as attachment areas for other stiffening members, if necessary.
With regard to the apparatus for vibrating the container, it has been found that application of the forces to the bottom of the container has the advantage of moving the bottom surface under the anodic material that would be supporting the bridge or arch, allowing the material to drop or descend.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.
REFERENCES:
patent: 2559926 (1951-07-01), Beebe
patent: 3300396 (1967-01-01), Walker
patent: 3862745 (1975-01-01), Chiz
patent: 4039403 (1977-08-01), Astley et al.
patent: 4059493 (1977-11-01), Rice
patent: 4077864 (1978-03-01), Vanderveer et al.
patent: 4197181 (1980-04-01), Portal et al.
patent: 4342635 (1982-08-01), Becker et al.
patent: 4569744 (1986-02-01), Walker
patent: 5340456 (1994-08-01), Mehler
patent: 5597460 (1997-01-01), Reynolds
patent: 5620586 (1997-04-01), Claessens et al.
patent: 5744013 (1998-04-01), Botts et al.
patent: 5766430 (1998-06-01), Mehler
patent: 5776327 (1998-07-01), Botts et al.
patent: 5938899 (1999-08-01), Forand
patent: 315481 (1929-07-01), None
Brodsky William Louis
Henderson Donald W.
Lehman Lawrence Philip
Bell Bruce F.
Fraley Lawrence R.
International Business Machines - Corporation
Schmeiser Olsen & Watts
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