U.S. patent number 3,862,891 [Application Number 05/399,894] was granted by the patent office on 1975-01-28 for uniform plating current apparatus and method.
This patent grant is currently assigned to GTE Automatic Electric Laboratories Incorporated. Invention is credited to Eugene C. Smith.
United States Patent |
3,862,891 |
Smith |
January 28, 1975 |
UNIFORM PLATING CURRENT APPARATUS AND METHOD
Abstract
A uniform plating current apparatus and method for providing a
nearly uniform flow of plating current within a plating tank
containing plating solution between a work piece to be plated and
an anode surface.
Inventors: |
Smith; Eugene C. (Elk Grove
Village, IL) |
Assignee: |
GTE Automatic Electric Laboratories
Incorporated (Northlake, IL)
|
Family
ID: |
23581390 |
Appl.
No.: |
05/399,894 |
Filed: |
September 24, 1973 |
Current U.S.
Class: |
205/96; 204/279;
204/DIG.7 |
Current CPC
Class: |
C25D
17/008 (20130101); C25D 17/12 (20130101); Y10S
204/07 (20130101) |
Current International
Class: |
C25D
5/00 (20060101); C23b 005/58 (); B01k 003/00 () |
Field of
Search: |
;204/297W,DIG.7,15,14,23,27,279 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
986 |
|
1896 |
|
GB |
|
587,445 |
|
Mar 1931 |
|
DD |
|
Primary Examiner: Tufariello; T. M.
Attorney, Agent or Firm: Lapacek; James V.
Claims
Having described what is new and novel and desired to secure by
letters
1. A uniform plating current apparatus for providing a uniform flow
of plating current in an electrolyte solution between a plating
rack carrying a work piece to be plated that forms a cathode and a
quadrangular anode structure, comprising:
two generally parallel surfaces of nonconductive composition
positioned along two opposite sides of the anode surface and
extending upwardly from the anode to the plating rack area; and
a first and second plurality of flow-blades running transversely
between said parallel surfaces and along the remaining two edges of
the anode structure, said first plurality of flow-blades spaced one
above the other along the distance between the anode surface and
the plating rack area and said second plurality of flow-blades
spaced one above the other along the
2. The uniform plating current apparatus of claim 1 further
characterized in that said first and second plurality of
flow-blades are generally
3. The uniform plating current apparatus of claim 1 further
characterized in that each successive flow-blade in the direction
from the object to be plated to the anode structure of said first
and second plurality of flow-blades is of increasing length so as
to extend farther toward the
4. The uniform plating current apparatus of claim 1 further
characterized in that the leading edges of said first and second
plurality of flow-blades extending into the electrolyte solution
are generally arcuately shaped so as to provide a smooth flow of
the electrolyte
5. The uniform plating current apparatus of claim 1 further
characterized
6. A method for providing uniform plating current flow in an
electrolyte solution between an anode structure and an object to be
plated which forms a cathode surface including the steps of:
positioning two generally parallel surfaces of nonconductive
composition along two sides of the anode structure extending
upwardly from the anode to the object to be plated; and arranging a
first and second plurality of flow-blades transversely between said
parallel surfaces and along the remaining two edges of the anode
surface, said first plurality of flow-blades spaced one above the
other along the distance between the anode structure and the object
to be plated and said second plurality of flow-blades spaced one
above the other along the distance between the anode surface and
the object to be plated.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of
electroplating and more particularly to a new and improved uniform
plating current apparatus and method.
2. Description of the Prior Art
In the plating of objects, particularly where the objects have a
large surface area or wherein a large number of components are
plated simultaneously in a single plating rack, the uniformity of
the plating thickness is difficult to control. The plating
thickness is especially important when plating such objects as reed
blades for reed relay capsules. The plating thickness distribution
in the electroplating process is a function of the plating current
that each particular component or portion of the object to be
plated receives from the anode. Uniformity of current flow and
preventing extraneous currents flowing near the periphery of the
work piece is essential where equal plating thickness is required.
A variety of approaches have been attempted in order to eliminate
unequal plating distribution utilizing shields and robber or thief
elements to absorb the extraneous current flows. Typical of a
shielding arrangement near the object to be plated is that
described in U.S. Pat. No. 2,675,348 which issued to L. Greenspan
on Apr. 13, 1954. Shielding means in order to affect uniform
plating is also described in U.S. Pat. No. 2,859,166 which issued
to J. C. Grigger on Nov. 4, 1958. A method and apparatus for
obtaining uniform plating on the bearing surfaces of
semi-cylindrical flanged bearings by the use of shields or baffles
positioned between the bearing and a slot communicating with the
anode is described in U.S. Pat. No. 2,751,340 which issued to R. A.
Schaefer et al. on June 19, 1956. The various attempts to obtain
uniform plating by means of shields and thief or robber elements
are not desirable where an extremely high degree of uniformity over
a large plating rack or object is desired. Uniform plating methods
utilizing shields cause blockage of the natural flow of electrolyte
solution with resultant turbulence effects which disturbs
uniformity of plating distribution. Further shielding techniques of
the prior art are very critical in their placement due to the fact
that shielding very near the surface of the object to be plated
causes complex current flow patterns which are difficult to measure
and maintain.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly it is a principal object of the present invention to
provide a uniform plating current apparatus and method for
providing a nearly uniform flow of plating current to obtain a
uniform plating distribution (throughout) the surface area of a
plating rack.
Another object is a uniform plating current apparatus that provides
unrestricted flow of the electrolyte solution in a plating tank
thereby eliminating turbulence conditions affecting the plating
process.
These and other objectives of the present invention are achieved by
providing two generally parallel surfaces of nonconductive
composition positioned along two sides of the anode surface that
extend upwardly from the anode to the plating rack area or object
to be plated. Further the apparatus comprises a first and second
plurality of flow-blades running transversely between the parallel
surfaces and generally along the opposite edges of the anode
surface. The flow-blades are spaced one above the other along the
distance between the anode surface and the plating rack area or
object to be plated.
Other objects will appear from time to time in the ensuing
specification drawings and claim.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the uniform plating current
apparatus of the present invention;
FIG. 2 is a front view of a plating tank in which no means is
provided for uniform current flow;
FIG. 3 is a front view of a plating tank in which two shields or
surfaces have been provided to obtain uniform current flow;
FIG. 4 is a front view of a plating tank in which flow-blades
similar to the present invention have been provided in order to
obtain uniform current flow;
FIG. 5 is a front elevational view of the plating apparatus of the
present invention;
FIG. 6 is a plan view of the apparatus shown in FIG. 5; and
FIG. 7 is a side elevational view of the apparatus in FIG. 5.
DESCRIPTION OF PREFERRED EMBODIMENT
The uniform plating current apparatus of the present invention
illustrated in FIGS. 1, 5, 6 and 7 includes a front retaining wall
10, a rear retaining wall 12, side walls 14 and 16 and a base 18.
Each of the side walls 14 and 16 includes a rectangular opening
bounded by edges 20, 22 and 24 as best shown in FIG. 7. Flow-blades
26, 28, 30 and 32 are carried by each of the side walls 14 and 16
and by the front retaining wall 10 and the rear retaining wall 12.
The flow-blades 26, 28, 30 and 32 may be secured by means of slots
in the material of the side wall 14, 16 and front retaining wall 10
and rear retaining wall 12 and/or by means of cement. The
flow-blades, as best shown in FIG. 5, are rectangular sheets of
varying lengths with the top flow-blade 26 mounted nearest the
upper most portion of the side walls 14 and 16 being the shortest
in length or overhang and each successive flow-blade 28, 30 and 32
being each of successively increasing length over the preceding
flow-blade. The leading edge or tip 34 of each of the flow-blades
26, 28, 30 and 32 is generally beveled or V-shaped. The function
and purpose of the leading edge 34 will be explained in detail
hereinafter.
Two plating rack guide pieces 36 are each mounted on the upper mosr
edge of the front retaining wall 10 and the rear retaining wall 12
whose function will be explained in detail hereinafter. The guide
pieces 36 are mounted to the front and rear retaining walls 10 and
12 by means of screws 38 although they may also be cemented.
Similarly the front retaining wall 10, the rear retaining wall 12,
the side walls 14, 16 and the base 18 may be secured by screws or
otherwise bonded together such as by means of cement. The uniform
plating current apparatus including walls 10, 12, 14 and 16 base
18, flow-blades 26, 28, 30 and 32, and guide pieces 36 may be
fabricated entirely from plastic of BAKELITE material although it
should be noted that other nonconductive material are also
suitable.
A conventional rectangular anode structure 40 is mounted on the
base 18 approximately midway between the side walls 14 and 16. A
conventional plating rack assembly 42 is supported by the uniform
plating current apparatus along the side walls 14 and 16 and the
front and rear retaining walls 10 and 12. The plating rack guide
pieces 36 including beveled surfaces 44 guide the plating rack into
position on the front and rear retaining wall surfaces. The plating
rack 42 and the uniform plating current apparatus are constructed
with appropriate dimensions so that the plating rack is positioned
securely between the side walls 14 and 16 and the guide blocks 36.
The plating rack 42 is designed to retain the object to be plated
or workpiece which may be a plurality of reed blades 46 as shown in
FIG. 5.
The various plating apparatus shown in FIGS. 2, 3 and 4 demonstrate
the various current paths found in plating tanks. The apparatus of
FIG. 4 shows the concept of the present invention to obtain a
uniform current plating distribution. The apparatus of FIG. 2
includes a plating rack 50 with a plurality of reed blades 52 to be
plated positioned in an electrolyte solution 54 contained by the
plating tank 56. A conventional anode structure 58 is mounted near
the bottom of a plating tank 56. A potential is applied between the
anode surface 58 and the reed blades 52 causing an ionic transfer
of plating current from the anode to the reed blades. The current
distribution of plating current is shown by straight current paths
60 between the anode 58 and the reed blade 52 and also by curved
paths 62 which swing out or curve from the anode surface to the
reed blades causing an unequal plating distribution due to
additional plating current delivered to the outer rows of the
plating rack 50 thus causing excessive plating.
To eliminate these extraneous currents, boundary planes 64 and 66
as shown in FIG. 3 may be added at each boundary of the plating
work piece or reed blades 52. This results in a current
distribution of straight current paths 60 and a uniform plating
current distribution with the extraneous current paths 62 of FIG. 2
being eliminated. While the addition of boundary walls or planes
such as 64 and 66 eliminates extraneous current paths, this also
causes turbulence and blocks the flow of the plating solution or
electrolyte which normally in constant agitation to provide for
consistent plating techniques.
The concept of the present invention as shown in FIG. 4 provides
uniform plating current distribution while allowing circulation of
the electrolyte solution without turbulence. Flow-blade surfaces
68, 70, 72 and 74 are utilized to provide a uniform current plating
distribution by means of a tapered arrangement and are positioned
to compensate for extraneous currents such as 76 that travel around
the anode 58 and the flow-blades and reach the reed blades 52. The
extraneous current paths are of minimal consideration due to their
increased resistance path. The overhanging arrangement of the lower
flow-blades 74 partially blocking the direct path from the anode
surface 58 to the reed blades 52 also provides compensation for the
small contribution of extraneous current paths to the overall
plating distribution.
The uniform plating current apparatus of the present invention as
shown in FIGS. 1, 5, 6 and 7 provides an equal plating distribution
along a work piece by means of maintaining a uniform plating
current distribution in an electolyte solution without preventing
the free flow of the electrolyte solution. A plurality of
flow-blades are provided to accomplish the uniform current
distribution. Front and rear retaining walls are provided along
those surfaces of the plating rack to maintain a uniform current
plating distribution in that dimension.
In a specific application of the present invention to plate a rack
of reedblades, the total range of plating thickness resulting among
the reedblade plating thickness was 80 to 90 microinches. The use
of conventional plating apparatus resulted in a range of plating
thickness of 80 to 130 microinches across the plating rack.
Whereas the preferred form of the invention has been shown and
described herein, it should be realized that there may be many
modifications, substitutions and alterations thereto without
departing from the teachings of this invention.
* * * * *