US2696466A

US2696466A - Method of electroplating

Info

Publication number: US2696466A
Application number: US121394A
Authority: US
Inventors: Jr John F Beaver
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-10-14
Filing date: 1949-10-14
Publication date: 1954-12-07
Anticipated expiration: 1971-12-07

Description

Dec. 7, 1954 J. F. BEAVER, JR

METHOD OF ELECTROPLATING Filed Oct. 14, 1949 Gttorneq United States Patent METHOD OF ELECTROPLATING John F. Beaver, Jr., Osborn, Ohio Application October 14, 1949, Serial No. 121,394

4Claims. (c1.204-23) This invention relates to electroplating processes and apparatus, and more particularly to a means and method of plating recessed, hard to plate, objects, although not necessarily limited thereto.

The electroplating of articles of complicated design, presenting crevices and other recessed surfaces, ordinarily is not attempted, particularly when a relatively heavy metal deposit is required. This is because in conventional plating methods prominent areas of the object become heavily plated while the recessed areas receive little if any of the metal deposit.

The object of the invention is to'simplify and improve the method as well as the means and mode of electroplating recessed objects, whereby such objects may not only .be economically manufactured, but will be more satisfactory, having a better deposit of plate thereon, such plate being substantially evenly deposited over the surface area of the object.

A further object of the instant invention is to advance the electroplating art by bringing objects of complicated design readily within the practice of the art.

Another object of the invention is to provide a method of and apparatus for evenly distributing a metal deposit of any desired thickness over a surface of irregular or complicated design.

A further object of the invention is to provide generally conventional electroplating apparatus incorporating an alternatively usable ability to plate objects having recessed, hard to plate areas.

Still another object of the invention is to present a new method of electroplating wherein there may simultaneously be carried out the steps of removing excess metal from heavily plated areas and of redistributing the removed metal over more lightly plated areas.

A still further object of the invention is to provide simplified apparatus for practicing the foregoing method.

A still further object of the invention is to introduce, and render practicable, the principle of bi-polarity of the object being plated.

A further object of the invention is to provide a method and apparatus for plating objects possessing the advantageous features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construct-ion, the parts and combinations thereof, and the mode of operation, as hereinafter described or illustrated in the accompanying drawings, or their equivalents. -In carrying out the above and other objects of the invention, a method of and apparatus for electroplating have been achieved involving use of one or more auxiliary anodes in the customary electroplating system, plus the use of adjustable polarity control means operable to produce in a first stage of operation a common polarity in the main and auxiliary anodes and an opposed polarity in the object and operable in a second stage to produce opposed polarities in the main and auxiliary anodes and in conjunction therewith to induce a bipolar condition in the object. In the practice of the invention, therefore, during the first stage of the operation the. object is plated in substantially the usual manner and as a result prominent areas acquire a heavy metaldepositwhile areas of lesser prominence are lightly coat- Then during the second 'stage of operation someiof the metal previously deposited on the promi ed, if at all.

2,696,466 Patented Dec. 7, 1954 nent areas is removed therefrom and redistributed over the recessed areas until both areas are evenly plated.

Referring to the accompanying drawing, wherein is found the preferred but obviously not necessarily the only form of embodiment of the invention,

Fig. 1 is a partly diagrammatic viewvof an electroplating installation electrically connected in accordance with the first stage of an operating cycle;

Fig. 2 is a view similar to Fig. 1, showing the parts electrically connected according to the second stage of the cycle;

Fig. 3 is a view similar to Fig. 2, showing an alternative connection to the object in the second stage of operation;

Fig. 4 is a view of an electroplating installation, showing the wiring diagram for obtaining the results in Figs. l and 2; and

Fig. 5 is a view similar to Fig. 4, showing the wiring diagram embodying the alternative connect-ion of Fig. 3.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawing, in the practice of the invention apparatus is utilized which includes a tank 10 substantially filled, as indicated, with an electrolytic solution. Immersed in the solution are a main anode 11 and one or more auxiliary anodes 12 made of the metal being deposited or any suitable conductor. An object to be plated is indicated at 13 and shown immersed in the solution. The object is an example of hard to plate articles, presenting prominent portions 14 projecting toward the main anode 11 and relatively remote recessed areas or corners 15. In setting up the apparatus for operation, the auxiliary anodes 12 are located in or close to the recessed areas while the main anode is spaced 2. conventional distance from the object.

Electrical conductors to connect the anodes and the object to be plated in an electrical circuit are provided, and in accordance with the instant invention, there is further provided polarity control means for initiating the successive stages of an electroplating cycle.

For illustrative purposes, the two alternating stage of the cycle are separately shown in diagrammatic form in Figs. 1 and 2. As shown in Fig. 1, in the first stage the main anode 11 and auxiliary anodes 12 are both connected to a conductor 16 leading from a suitable source of electrical current and representing the positive side of such current source. Object 13 is connected to a conductor 17 leading from the same current source and representing the negative side thereof. According to the first stage of operation, therefore, a substantially conventional electroplating operation takes place in response to closing of the electrical circuit.

The

elements

11 and 12 function as anodes and the object 13 as the cathode with the result that metal is deposited on the object. The first operational stage is continued for a period of time sufficient to produce a substantial deposit of metal on the prominent surfaces of the object. Then the circuit is opened, interrupting the plating action, and adjustments of polarity made to condition the apparatus for second stage operation, as shown in Fig. 2.

According to this arrangement, the main anode 11 is connected to negative conductor 17, auxiliary anodes 12 remain connected to positive conductor 16 and object prominent areas is removed and the deposit on the recessed areas 15 is increased. It is believed that the action WhlCh takes place in this stage is one of redis tributing metal taken from the prominent surfaces and I a deposit of metal on the recessed surfaces. 7

The second operational stage is discontinued after a determined interval and may be repeated, if necessary, until}. an :evenplating' of desired thickness; is obtained Aoverthe entire surface of, the object. The-time of each- In response to closing of the cir-.

stage of the cycle is varied according to plating thickness desired and the structural detail -of-theobject being plated,

the second or bi-polar stage. being usually of shorter duration, and with higher voltage, than the first stage.

In some;cases, during the. bi-polar ,stage of the cycle,.,-,

it may; be advantageous. to. connect; the. :object beingplated :througha resistance to the... positive side of the current source.

without, however, altering its cathodic relationship to The result obtained is to make: the ob.- ject more anodic to the cathode (normalyanodell) auxiliary anodes. 12. Such an arraugementis shownin I Fig. 3 wherein a tank 18, main anode 19, auxiliary anode- 21, object 22, positive conductor 23. and negative conductor 24 occupy the same relationship as the corre-v sponding elements of the embodiment of Figs. 1 and-2. .1

In .-this.instance, however, in the second stage of operation, which .is that shown, the object 22. is connected to positive conductor 23 by a lead incorporating a variable resistor 26.

Considering .the .means for changing polarity in .the

Arrangements of this a switch 27. Through these arms positive conductor 16.v

is permanently connected to a contact 23 and negative conductor 17 is-permanently connected toa contact 29. A lead 31 extends from contact 28 tothe auxiliary anodes 12' so that these anodes are continuously connected to the positive side of the current source. Contacts 32 on respective arms of switch 2'7 are alternatively engageable with a pair of spaced contacts 33 and 3 5 and another pair of spaced contacts and 36. Thus the contact 32 on that switch arm which is positive by reason of-its connection with conductor 16 is alternatively engageable with contacts 33 and 35. Contact 33 is connected by a lead 37 with the main anode 11. Contact 35 has no electrical connection. Contact'36 is connected bya lead 39 with lead 37 and thereby to the main anode 11.

In the operation of the apparatus, the switch 27 normally stands in an upright or neutral position and the electrical circuit is open. To initiate the first stage of the electroplating operation, the switch 27 is moved from neutral to a position engaging contacts 32 with

contacts

33 and 34 respectively. A circuit thereby is closed from conductor 16 through parallel leads 31 and 37 toanodes 11 and 12, through theelectrolytic bath, object 13 and lead 38 back to negative conductor 17. the-first stage of operation and initiate the second, switch 27 is returned to neutral position and its throw in that direction continued until the contacts 32 respectively engage contacts 35 and 36. A circuit then is closed from positive conductor 16 through lead 31 to the auxiliary anodes 12, through the bath to the recessed sur- To discontinue faces 15 of the object 13 and from the prominent sur- 1 faces 14 of the object through the bath to main anode 10 (now cathodic) and by way oflead 39 back to negative conductor 17.

ception, and so will not be individually described. The exception resides, as noted in the description referring 4 possessing the particular features of advantage before enumerated as-desirable, -but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to thespecific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the inven tion into effect,

Having thus described my invention, I claim:

1. A method of electroplating irregularly shaped objects, including the steps of immersing the object to be plated in an electrolytic bath, further inserting in the bath at least two anodes, one of said anodes constituting an auxiliary anodeandbeing placed in a recessed area of. the object, another .of said anodes constituting the main anodeand. placed outsideof the object spaced from said auxiliary anode and with thesaid auxiliary anode being positioned between the object and said main-anode, connecting said anodes to a source of current on the positive side, connecting said object to the current source on the negative side, applying current through the circuit so established for a determined time interval, interrupting current flow, disconnecting said object from the current source, reversing the electrical connection of said main anode from the positive side to the negative side while maintaining the connection of said auxiliary anode to the positiveside, and applying current through the circuit so established for a second determined time interval.

2. A method of electroplating objects presenting recesscd, hard to plate, areas, including the steps of immersing the object to be plated in an electrolytic bath, furtherinserting into the bath at least two anodes, one of said anodes constituting an auxiliary anode and being placed in a recessed area of the object, another of said anodes constituting the main anode and placed outside of the object, spaced from said auxiliary anode and with the said auxiliary anode being positioned between the object and'said main anode, and carrying out a two-stage electroplating cycle involving a changing of polarity, in the first of which stages said main and auxiliary anodes are anodic while said object is cathodic and in the second of which the main anode is cathodic, the auxiliary anodes are anodic and the object is bi-polar, the recessed areas being cathodic with respect to the auxiliary anodes and the more prominent parts of the object being anodic with respect to the main anode which in the second. or reversed stage is the cathode.

3. Electroplating apparatus, including a tank to receive the object to be plated, main and auxiliary anodes mounted in said tank, means for suspending an object, said object to be plated in the tank, separate electrical conductors between each of said anodes and a current source and between said object and said current source, and switch means controlling flow through said conductors, settable to afirst position to connect said anodes to thepositive side of thecurrent source and said object to Fig. 3, in the connecting of the object to the positive side of the current source during the second stage of operation. tioned to correspond to contact 35 of Fig. 4. Unlike contact 35, however, which is electrically unattached in In Fig. 5, therefore, a contact 41 is posi- 1 the system, contact 41 is connected by lead 25 incorpo-1 rating resistor 26 to lead 42 connected to the object 22.

Accordingly, when the switch is thrown to initiate the second stage of operation, object 22 is directly connected through resistor 26 to the positive side of the. current source.

Itjis-to be noted that conventional plating can be carried out on the apparatus of the invention simply by omitting the second operational stage. The switch 27 then functions as a simple on-off control, moving between neutral position and a position engaging-contacts 32 with

contacts

33 and 34.

From the above description it will't beapparent?thatofl thereis thus provided-a deviceof the character describe'd.

to the negative side of the current source and settable to a secondposition to connect said main anode to the negative side'of the current source, the auxiliary anode to the positive side and to disconnect said object from the current source.

4.- Electroplating apparatus, including a tank to re ceive the object'to be plated, main and auxiliary electrodes mounted in said tank, means for suspending an object, 'saidobject to be plated in the tank, separate electrical conductors between each of said anodes and a current source and between said object and said current source, switch means controlling flow through said conductors settable from a first position in which said anodes are'connectcd to the, positive side of the current source and the object is connected to the positive side of the current source andthe object is connected to the negative-,side -of-the current, source to a second position in whighthe-rnain ancdeisconnected to the negative side,

and a resistor included in the electrical connection of Number said object to the current source in the said second posi- 2,119,936 tion of said switch means. 2,451,341

References Cited in the file of this patent 5 UNITED STATES PATENTS gg f Number Name Date 1,526,644 Pinney Feb. 17, 1925 1,534,709 Holt Apr. 21, 1925 10 1,566,265 Antisell Dec. 22, 1925 1,951,893 Winkler Mar. 20, 1934 6 Name Date 'te June 7, 1938 Jernstedt Oct. 12, 1948 FOREIGN PATENTS Country Date Great Britain Sept. 15, 1930 OTHER REFERENCES The Monthly Review, Apr. 1942, pages 301-308. Metal Finishing, Oct. 1942, pages 524-526.

Claims

1. A METHOD OF ELECTROPLATING IRREGULARLY SHAPED OBJECTS, INCLUDING THE STEPS OF IMMERSING THE OBJECT TO BE PLATED IN AN ELECTROLYTIC BATH, FURTHER INSERTING IN THE BATH AT LEAST TWO ANODES, ONE OF SAID ANODES CONSTITUTING AN AUXILIARY ANODE AND BEING PLACED IN A RECESSED AREA OF THE OBJECT, ANOTHER OF SAID ANODES CONSTITUTING THE MAIN ANODE AND PLACED OUTSIDE OF THE OBJECT SPACED FROM SAID AUXILIARY ANODE AND WITH THE SAID AUXILIARY ANODE BEING POSITIONED BETWEEN THE OBJECT AND SAID MAIN ANODE, CONNECTING SAID ANODES TO A SOURCE OF CURRENT ON THE POSITIVE SIDE, CONNECTING SAID OBJECT TO THE CURRENT ON THE ON THE NEGATIVE SIDE, APPLYING CURRENT THROUGH THE CIRCUIT SO ESTABLISHED FOR A DETERMINED TIME INTERVAL, INTERRUPTING CURRENT FLOW, DICONNECTING SAID OBJECT FROM THE CURRENT SOURCE, REVERSING THE ELECTRICAL CONNECTION OF SAID MAIN ANODE FROM THE POSITIVE SIDE TO THE NEGATIVE SIDE WHILE MAINTAINING THE CONNECTION OF SAID AUXILIARY ANODE TO THE POSITIVE SIDE, AND APPLYING CURRENT THROUGH THE CIRCUIT SO ESTABLISHED FOR A SECOND DETERMINED TIME INTERVAL.