U.S. patent number 3,780,247 [Application Number 05/254,815] was granted by the patent office on 1973-12-18 for contact element having noble wear area.
This patent grant is currently assigned to The Bunker-Ramo Corporation. Invention is credited to Robert M. Healy, Ralph J. Hovey.
United States Patent |
3,780,247 |
Healy , et al. |
December 18, 1973 |
CONTACT ELEMENT HAVING NOBLE WEAR AREA
Abstract
A method and apparatus for making electrical contact members
from a continuous sheet or tape of electrically conductive
material, the members being provided with precisely located plated
wear areas adapted to establish electrical connection with a mating
contact. Apparatus is provided for indexing the tape with
longitudinally spaced apart locating pilots, and for coating the
tape with a resist material in a manner to define a precisely
located non-coated areas thereon, the non-coated areas
corresponding to the wear areas of the contacts. Thereafter, the
tape is subject to a selective plating process which plates only
the non-coated wear areas with a layer of noble metal. Cleaning
apparatus is provided for removing the resist material from the
tape, and apparatus is provided for punching and forming the
contacts from the tape, the apparatus being operative to precisely
fixed the plate wear areas of the contacts with respect to the
indexing pilots. In this manner, each of the contacts formed is
provided with a precisely located plated wear area .
Inventors: |
Healy; Robert M. (Warrenville,
IL), Hovey; Ralph J. (Glen Ellyn, IL) |
Assignee: |
The Bunker-Ramo Corporation
(Oak Brook, IL)
|
Family
ID: |
22965695 |
Appl.
No.: |
05/254,815 |
Filed: |
May 18, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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815609 |
May 14, 1969 |
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Current U.S.
Class: |
200/267 |
Current CPC
Class: |
H01R
43/16 (20130101); C25D 5/02 (20130101) |
Current International
Class: |
C25D
5/02 (20060101); H01R 43/16 (20060101); H01h
001/06 () |
Field of
Search: |
;200/166A-166M
;29/630,63C ;113/119 ;204/206 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Miller; J. D.
Assistant Examiner: Fendelman; Harvey
Parent Case Text
This is a continuation, of application Ser. No. 815,609, filed Apr.
14, 1969 now abandoned.
Claims
1. An electrical contact element suitable for use as one of a
plurality of contact elements in an electrical connector assemblage
mateable with another connector assemblage having a mating contact
element, said electrical contact element comprising a conductive
member having a limited surface area thereof designated for active
wearing engagement with another electrical contact element,
a relatively hard layer of noble metal corresponding in structure
to an electrolytically deposited form of that metal upon the
material comprising said conductive member affixed to said limited
area only, said layer being substantially thicker than the heaviest
layer of that noble metal which is suceptible of being deposited
upon the surface of said member by means of a self limiting
immersion ion exchange plating process, and,
upon substantially all of the surface area of said member not
covered by said first mentioned layer, a relatively soft
substantially uniform layer of a noble metal the structure of which
corresponds to a self limiting immersion ion exchange deposition of
that noble metal upon the material comprising said conductive
member, as distinguished from an electrolytically deposited form of
that noble upon said material.
2. A contact element in accordance with claim 1 wherein the metal
of the first mentioned layer is gold.
3. A contact element in accordance with claim 1, wherein the
thickness of the first mentioned layer is in the order of 30 micro
inches, and the thickness of the soft layer is in the range of 2 to
5 micro inches.
4. A contact element in accordance with claim 1, wherein the
thickness of the first mentioned layer is at least 5 times the
thickness of the soft layer.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to manufacturing electrical
contact members, and particularly to a fabricating process and
apparatus for rapidly and economically producing large quantities
of selectively plated contact members in a continuous manner.
An electrical contact member generally has a terminal portion to
which a conductor or wire may be electrically connected, and an
engagement portion and surface adapted to mechanically engage and
mate with a similar portion and surface of another contact member.
With use of the contact members, the engagement surface becomes the
active area of the contact, subject to substantial wear. In the
position in which two contact members are fully mated or engaged,
this engagement or wear area must be substantially free of
contamination or oxides which inhibit the flow of electrical
current between the two contacts. For this reason, electrical
contacts have been plated with costly, non-corrosive nobel metals
such as gold, using generally conventional plating processes and
apparatus.
Heretofore the conventional method of plating large quantities of
contact members has been the barrel type of process in which a
large number of the contact members are placed in a perforated
vessel which is rotated in an electrolytic plating solution of
noble metal. A negative potential is applied to the contacts by a
conductor or electrode which hangs loosely in the vessel. As the
vessel rotates, the contact members tumble therein and
intermittantly come into contact with the electrode. Plating
current thereby passes to those members which directly contact the
electrode as well as those which in turn physically touch such
members. The members, however, that are not in physical contact
with the electrode or with other members that are in contact
therewith, receive no plating current. Thus, plating current tends
to be non-randomly applied to the contact members during a barrel
type plating process. For this reason, the thickness of the
deposited metal is not uniform from member to member.
Moreover, contact members are preferably made from spring metals
such as cadmium bronze. When cadmium bronze is placed in a gold
plating solution and no electrical potential is applied to the
bronze the cadmium tends to enter and contaminate the plating
solution. To avoid such contamination, the sheet metal from which
the contact members are made has heretofore been first plated with
a layer of copper to prevent the cadmium of the cadmium bronze
metal from coming directly into contact with the gold plating
solution.
When plating contact members of the type described the barrel type
of plating process is not economical of the plating metal in that
the entire surface of each contact member is plated rather than
just the wear area. If the plating metal is a precious metal such
as gold, the cost and waste of such a plating process can be quite
substantial.
A more recent approach to the problem of selectively coating large
numbers of electrical contacts is disclosed in U.S. Pat. No.
3,137,645, issued to R. T. Vaughan et al. on June 16, 1964. The
vaughan et al. patent discloses apparatus wherein a limited area of
a contact member is plated, the plating being accomplsihed by
action of jet streams of electrolyte plating solution directed
thereagainst. The jet streams are provided by a plurality of
nozzles, and a chain of the contact members is conducted past the
nozzles for the plating operation. While the Vaughan et al
apparatus does not plate the entire contact member the spraying
action prevents sharply defined plated areas from being formed.
Consequently, to ensure that a given thickness of metal will be
deposited on a given wear area of a contact member it is necessary
to employ a nozzle which produces a jet stream having an effective
area substantially larger than the wear area. This is, of course,
wasteful of the metal in the plating solution.
A further problem with the Vaughan et al process is that of cadmium
contamination of the gold plating solution as explained above with
respect to the barrel type of plating process. Vaughan et al
gravity feed their plating nozzles from a reservoir of the plating
solution located above the nozzles. In the event of the loss of
plating potentials, the plating solution would continue to be
directed against the contact members, with the possibility of the
cadmium in the contact members entering into the solution of the
plating metal.
BRIEF SUMMARY OF THE INVENTION
Broadly, the present invention comprises a method an apparatus
capable of rapidly and economically mass producing large quantities
of electrical contact members having plated portions precisely
located on the active wear area and surface of each member. This is
accomplished by first providing a sheet or tape of electrically
conductive material, the sheet or tape being of such a dimension
that successive incremental lengths thereof serve as a plurality of
interconnected blanks from which the contact members are formed.
The tape is next continuously provided with longitudinally spaced
locating indices or pilots, and then continuously, selectively
coated with a resist material in a manner to define non-coated or
bare areas thereon corresponding to the wear areas, the non-coated
areas being precisely located with respect to said locating pilots.
The tape is next continuously subjected to a plating solution of
noble metal, said metal adhering only to the non-coated areas of
the tape to form plated wear areas thereon. The resist material is
then removed from the tape and the incremental lengths of the tape
are subjected to a forming and punching operation. The apparatus
for performing this operation engages the locating pilots in a
manner to accurately locate the plated wear areas with respect to
the pilots so that as each contact member is formed it is provided
with a precisely located plate wear area with respect to the
remaining portions of the contact member. Preferably, after the
contacts are formed and separated from the tape, they are plated
with an extremely thin layer of noble metal by an electroless
plating operation to prevent the member from future tarnishing and
oxidation.
The invention, as only briefly described thus far, provides a
highly economical method of plating electrical contacts that is
particularly useful when the plating metal is a precious metal such
as gold.
THE DRAWINGS
The invention, with its objectives and advantages, will be best
understood from consideration of the following detailed description
taken in connection with the accompanying drawings in which:
FIG. 1 is an enlarged side elevation view of a contact member
fabricated in accordance with the principles of the invention;
FIG. 2 shows apparatus for performing at least the initial step of
the invention through which an electrically conductive tape is
provided with locating indices or pilots;
FIG. 3 is a plan view of the tape produced by the apparatus of FIG.
2;
FIG. 4 is a diagrammatic representation of a punching die embodied
in the apparatus shown in FIG. 2;
FIG. 5 diagrammatically illustrates apparatus for performing a
following step of the invention in which the tape is selectively
coated with a resist material;
FIG. 6 shows the tape coated with the resist material;
FIG. 7 diagrammatically illustrates apparatus for performing
further steps of the inventive process in which the tape is
continuously, selectively plated and the resist material is
thereafter continuously removed from the tape;
FIGS. 8 through 8B represent various forms which the tape
successively takes during yet another step of the invention in
which electrical contact members are formed from the tape;
FIG. 9 shows apparatus for forming the contacts of FIG.8;
FIG. 10 shows means for performing a final plating step.
PREFERRED EMBODIMENT
Specifically, FIG. 1 is an enlarged side view of a plated metallic
contact member 10 made in accordance with the principles of the
invention. The contact 10 is of the type and configuration shown
and described in U.S. Pat. No. 3,002,176, issued Sept. 26, 1961, to
R. S. Yopp and assigned to the present assignee. Such contact
members are made from a spring metal, such as cadmium bronze, and
have mounting shank and terminal portions 12 and 14 respectively,
and a contact engaging blade portion 16. The mounting and terminal
portions are formed to have a three-sided channel shape adapted to
seat in a cavity formed in a molded insulating connector, for
example, as shown in the above-mentioned Yopp patent. The terminal
portion 12 is adapted to be joined with an electrical conductor or
wire (not shown). The blade portion 16 is formed to engage and mate
with a similar blade portion of an opposite contact member in an
active wear area defined by a layer of noble metal 17 deposited on
a convex surface 18 of the blade in accordance with the princples
of the invention as hereinafter explained. The blade 16 is further
provided with a smoothly rounded convex bulge or protuberance 20 on
the convex surface portion 18 thereof so that the wear area of the
blade includes the protuberance 20.
The layer of noble metal 17 on the blade 16 must be of a thickness
sufficient to insure against the metal of the blade surface 18 from
becoming exposed to the atmosphere. When oxidation begins to form
even in an extremely small portion of the wear area, the small
portion becomes a source of contamination from which oxidation
substances are spread to the remaining portions of the wear area.
The spread of the contamination is brought about when the use of
the contact member is placed in or removed from mating engagement
with an identical or another contact member.
FIG. 2 shows apparatus for beginning the process of the invention.
More particularly, FIG. 2 shows a punch press 22, a tape 24 of
spring metal material, such as cadmium bronze, being continuously
directed through the press from a feed reel 28 to a take-up reel
29. Between the press and the take-up reel is located a vessel 30
through which the tape is conducted, the vessel representing a
means for cleaning the tape.
The punch press 22 provides the tape with indexing or locating
pilot holes 25 as shown in FIG. 3. This is accomplished by a
punching die 26 separately depicted in FIG. 4, the die 26 being a
part of the punch press 22.
The punching die 26 comprises essentially a tapered locating pin
26a and a punching or perforating pin 26b, the locating pin being
longer than the punching pin. The tape 24 is successively advanced
through the die to undergo the punching process, the locating pin
26a fixing the position of the tape for the punching pin 26b. In
this manner, the pilot holes are formed and located in exact
spacial relationship to each other in a longitudinal direction.
The tape 24 is further fed through the punch press 22 and through
the die 26 with one edge of tape in sliding engagement with an edge
or guide 26c, the edge or guide being shown in elevation in FIG. 4.
In this manner, the engaged edge of the tape functions as a fixed
reference for the lateral displacement of each pilot hole 25.
The holes 25 provided in the tape 24 act as locating indices or
pilots which function to precisely locate the tape in the various
operations to be performed thereon. Although preferably in the form
of apertures or slots these indices may be simply printed or
embossed areas which are electrically, photometrically or
mechanically sensed in effecting the desired locating function.
Successive incremental lengths 24' (FIG. 8) of the tape 24 as thus
far described, serve as a plurality of interconnected blanks from
which pluralities of contact members 10 (FIG. 1) are formed and
punched in a manner explained hereinafter.
FIG. 5 shows diagrammatically apparatus for performing the next
step of the invention. Specifically, FIG. 5 shows a printing
apparatus 32 having printing rollers 34, a drying means 36, and
feed and take-up reels 37 and 39 respectively. The tape 24, after
being indexed and cleaned by the process and apparatus of FIG. 2,
is conducted through the printing rollers 34 in a continuous manner
by drive means (not shown) driving the take-up reel 39. The rollers
34 are adapted to coat the tape with a resist material on all areas
thereof where a layer of a noble plating metal is not desired. More
particularly, at least one of the rollers is provided with a
pattern having a dimension corresponding to the plated wear area 17
of the contact member 10, the roller applying the resist material
in a manner to define the wear areas in discrete, non-coated or
bare areas 40 as shown in FIG. 6. The non-coated areas 40 are
precisely located with respect to the indexing holes 25 by virtue
of indexing projections 38 (only representively shown and provided
on the upper roller in FIG. 5), the projections engaging the holes
25 as the tape passes through the rollers. The projections are
precisely located with respect to the pattern on the printing
roller to effect the precise location of the non-coated areas
40.
In a preferred embodiment of the invention the rollers 34 coat one
side of the tape and both edges thereof completely with the resist
material, whereas the other side of the tape is provided with two
rows of the non-coated areas 40 as shown in FIG. 6. In this manner,
the blank from which the contact members will be formed, includes
the area of the tape encompassing two side-by-side non-coated or
bare areas 40 and an associated pilot hole 25. From each blank, two
contact members 10 will be formed and separated from the tape in a
manner explained hereinafter. The number of contact members formed,
however, from each blank may be one or more than two depending upon
the dimensions of the tape and the contact members to be formed
therefrom.
After the resist material is applied to the tape 24, the material
is dried and hardened thereon by the drying means 36, only
representively shown in FIG. 5, the tape being collected on the
reel 39.
The resist material employed in the coating process may be any
material capable of being continuously applied and will adhere to
the tape during the future selective plating process, yet can be
removed from the tape after the plating process. An example of such
a material would be removable ink such as flexographic printing
inks which are well known in the printing art, though the invention
is not limited thereto.
In a similar manner, the apparatus 32 may be any device capable of
applying the resist material in a controlled, continuous manner,
for example, a flexographic printing press such as model 416 Webron
labelling machine, though other devices may be used.
FIG. 7 shows, schematically, apparatus for performing the next
successive steps in the inventive process as thus far described.
More particularly, FIG. 7 shows enclosures or containers 41 for
performing continuously an additional cleaning operation upon the
tape as it is removed from a feed reel 41a and before it is
conducted to an electrolytic plating apparatus 42. Thereafter, the
resist material is continuously removed from the tape in enclosures
or containers 44 located downstream from the plating apparatus 42,
before being collected on a takeup reel 45.
The plating apparatus 42 is schematically represented by an
enclosure or tank 47 containing an anode plate or grid 48
electrically connected to the positive side of a direct current
power supply 49. The negative side of the power supply is
electrically connected to the tape 24 by a tape contacting brush
(only representatively shown by a circle 50 in FIG. 7) located
downstream of the containers 44 employed for removing the resist
material. In this manner, a bare tape is available for making good
electrical contact with the brush thereby making the tape a cathode
for the plating process. Beneath the tank 47 is located a container
52 containing an electrolytic solution of noble plating metal. The
solution is directed to the enclosure 47 from the container 52, and
returned thereto after the plating process for subsequent plating
use, the container serving as a reservoir of the plating metal and
solution.
In the plating process, the tape 24 is continuously conducted
through the plating tank 47 and through the solution of noble metal
contained therein. With a positive potential applied to the anode
48, and a negative potential applied to the tape via the brush 50,
plating current is conducted through the solution to the bare,
non-coated areas 40 of the tape to deposit the noble metal only on
said areas, the coating of resist material functioning as an
electrically resistive and substantially non-conductive material
which prevents plating on those surfaces of the tape covered by the
resist material. The plating metal deposits in a substantially
uniform manner on the non-coated areas 40 to form the layer 17
(FIG. 1) having a desired thickness dimension a desired thickness
dimension being preferably in the order 30 micro inches.
As can readily be appreciated, the only plating metal used in the
present selective plating process is the metal applied to the wear
areas of the contact. Substantially no metal is wasted, the plated
metal being confined to the area of the contact where it is needed,
namely, the wear area.
Thus, when plating precious metals such as gold, substantial
savings may be realized through the use of the present invention in
contrast to prior art methods.
The solution of noble metal employed in the plating process of the
present invention is preferably a hard, cobalt gold solution made
from potassium gold cyanide. An example of such a solution is the
Autronex C I Process Solution manufactured by the Sel Rex
Corporation of Nutely, New Jersey, though other hard gold solutions
are available and can be used. A hard gold is preferable for the
active, wear area of each completed contact 10 to insure that the
wear area remains completely provided with a non-corrosive,
non-oxidizing metal during the life of the contact member or
connector in which the member is employed.
During the plating process, as long as the potentials are properly
applied to the anode 48 and the tape 24, and current flow is in the
direction of the tape, the cadmium in the metal of the tape will
not dissolve to any meaningful extent in the gold solution to
contaminate the solution, the direction of plating current tending
to maintain the cadmium in combination with the copper of the tape
as explained earlier. If, however, the application of the
potentials is interrupted during the plating process, a means is
provided for automatically draining the solution of gold from the
plating tank 47 before the cadmium has opportunity to dissolve in
and contaminate the gold solution. Such an automatic draining means
may include a sensing relay 53 (only representatively shown in FIG.
7) electrically connected in the circuit of the power supply 49,
and operative to effect the release of the plating solution to a
container 53A when the relay senses the absence of plating current.
From the container 53A the solution may be returned to the
reservoir container 52 in a suitable manner. For this reason, in
the present invention, it is not necessary to plate a cadmium
bronze tape with copper in order to prevent cadmium contamination
of the gold solution.
In FIG. 7, the apparatus for cleaning the blanks and for removing
the resist material employs liquid spray nozzles located within the
containers 41 and 44 for directing suitable cleaning liquids
against the blanks though other means be employed in place thereof
or in conjunction therewith. A suitable cleaning fluid would be
normal alcohol which is a common, well-known solvent for ink in the
printing industry.
The tape may be drawn through the containers 41, 44 and the plating
tank 47 by a suitable drive means, for example, by positive
friction drive rollers 54 only diagrammatically indicated in FIG.
3. The rollers may be driven by a variable speed motor (not shown)
connected to further drive the take-up reel 45 in a manner which
maintains suitable tension on the tape.
By controlling the speed at which the tape 24 is pulled through the
plating tank 47 and/or by controlling the potential difference
between the tape and the anode plate 47, the desired thickness of
the metal plate can be precisely controlled.
After the non-coated or bare areas 40 are plated and the tape is
collected on the take-up reel 45, the tape is ready for the process
of punching and forming the completed, individual contact members
10.
In FIG. 9, a device 56 for performing this process is
diagrammatically depicted, the device being a punch press 56 having
contact forming and punching dies 57. The press and dies operate in
a manner to preciesely locate the area of each contact member on
the tape before the contact is formed and separated from the tape.
The dies 57 form and punch the contact members in successive pairs
from the tape, and the process by which the dies accomplish this 10
is indicated in FIGS. 8 to 8B. The punch press moves successive
incremental portions 24' of the tape 24 from a feed reel 55 through
its punching dies 57 in successive steps during which portions of
the metal encompassing the contact area are successively punched
away. The tape is precisely located in the dies by the successive
engagement of two pins of a pilot punch cooperating with an edge
guide (not shown). The spacing of the pins relative to each other
and to the edge guide are the same as those of the punching die 26
shown in FIG. 4. In this manner, the contacts are precisely located
with respect to the indexing pilots so that when the contacts 10
are finally formed and severed from the tape, the plated wear area
17 of each contact member 10 is precisely located with respect to
the remaining portions of the contact member.
As the contact members 10 are formed in pairs, as shown in FIGS. 8A
and B, and the metal is cut away by the dies 57, a portion 58 of
each blank associated with a pilot hole 25 serves essentially as a
carrier portion which carries each pair of contacts until the
contacts are finally severed therefrom. The severed, completed
contacts are collected in a container 59 as shown in FIG. 9.
The punch press 56, and the operation thereof, as described above,
is basically that of a multi-slide machine manufactured by the
United States Tool Company. In the present invention, however,
other types of contact member forming machines and devices may be
used without departing from the spirit and scope thereof.
After the contact members 10 are formed and separated from the tape
24, the unplated portions of the contact members are plated with an
extremely thin layer of a noble metal in order to prevent the
members from future tarnishing. A suitable thickness for the thin
layer would be on the order of two to five micro inches. This is
accomplished by an electroless, immersion type of plating process
as diagrammatically indicated in FIG. 10, the contact members being
placed in a basket 60 or other suitable container and lowered into
a solution 62 of the plating metal.
An electroless plating process is a preferential plating process in
which the noble metal, (for example, a substantially pure, soft
gold) exchanges places with the metal of the part to be plated on
an ion exchange basis. This is to be contrasted with an immersion
type plating process in which a catalyst or reductant is employed
whereby the deposition process is not self limiting. The thickness
of the plating produceable by this type of process is limited as in
the case of gold to a few micro inches since the heavier the
deposition of the gold on the part the more the electroless plating
process is inhibited. The electroless process is particularly
suitable for purposes of the present invention since the thickness
of the plating is substantially that required to provide the
non-tarnishing, thin layer of soft gold over the portions of each
contact members not covered by the heavier layer of noble metal 17.
The electroless type of plating operation is a well-known process,
and there are a variety of gold solutions available for this type
of plating process.
In the description of the present invention, the term noble metal
is representative of any substantially inert, non-corrosive or
non-oxidizing metal suitable to maintain the surfaces of the
contact members 10 free from contaminating substances which would
adversely affect their ability to conduct electrical current when
disposed in mating engagement with other contact members.
From the foregoing description it should now be apparent that the
present invention provides a new and useful process and apparatus
for rapidly and continuously fabricating plated electrical contact
members in an economical manner. This is accomplished by first
providing a continuous tape of spring metal material with locating
pilots. The tape is next continuously directed through a coating
device, the coating device applying a resist material to the tape
in a manner to precisely define bare areas thereon corresponding to
wear areas of the contact members. Thereafter the tape is
continuously subject to a plating process in which a layer of noble
or other non-corrosive metal is applied to the bare areas only. The
resist material is continuously removed from the tape and the tape
is next subjected to a contact forming operation in which the
plated wear areas are successively and precisely fixed with respect
to the locating pilots before the contact members are formed and
punched from the tape. In this manner, each completed contact
member is provided with a plated wear area that is precisely
located with respect to the remaining portions of the contact
member.
Though the invention has been described with a certain degree of
particularity, changes may be made therein without departing from
the spirit and scope thereof. What is claimed is:
* * * * *