US3697405A

US3697405A - Apparatus for partial electroplating including an electroplating head

Info

Publication number: US3697405A
Application number: US873376A
Authority: US
Inventors: Karl Butter; Willibald Wittich
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1968-11-07
Filing date: 1969-11-03
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: DE1807481C3; FR2022793A1; DE1807481B2; GB1288089A; DE1807481A1

Abstract

A process for partial electroplating using a plating head carrying the anode and which is traversed by the electrolyte is characterized by the fact that it proceeds continuously with the exclusion of air or oxygen. The electrolyte is supplied from an electrolyte tank by means of a pump unit through a hose system to the plating head which is pressed against the article to be plated so that the article therefore acts as a cathode. The ends of the hose system for the head are immersed in tanks which may be filled for example, with cleaning liquid or an etchant and may be thereafter connected with gas tanks and the electrolyte as desired. The apparatus includes hose pumps comprising rotating members which cyclically operate upon a portion of the hoses connected to the electrolyte or the fluid for the purpose of directing the electrolyte or fluid from a tank source up to the electroplating head. The head is held against the article for example, a boiler which is to be electroplated with the interposition of a sealing material. Within the plating head the direction of the flow of the electrolyte is opposed so that the electrical current and the anode is located behind the cathode in respect to the flow direction, precious metal electrode which is insoluble in the electrolyte may also be used so that the material to be deposited is then taken only from the electrolyte.

Description

. Oct-10, 1972 K UT ETAL 3 697,405

APPARATUS FOR PARTIAL ELECTROPLATING INCLUDING AN ELECTROPLATING HEAD Filed Nov. 5, 1969 2 Sheets-Sheet 1 Fig.1

4 3 b x J 52 2; a 2; O x q 7 mvemcfi A Karl Butter Willibald Wittich OcblO, 1972 BUTTER ETAL N I D U L C N I G m TA mm We R Tm mm L m L A m NC m w R A F S U T A R A P P A 2 SheetsSheet 2 Filed Nov. 3, 1969 v AMI/2f r Fig. 2

United States Patent 3,697,405 APPARATUS FOR PARTIAL ELECTROPLATING INCLUDING AN ELECTROPLATING HEAD Karl Butter, Munich, and Willibald Wittich, Ottobrunn, Germany, assignors to Messerschmitt Bolkow-Blohm Gesellschaft mit beschrankter Haftung, Munich, Ger- Filed Nov. 3, 1969, Ser. No. 873,376 Claims priority, application Germany, Nov. 7, 1968, P 18 07 481.2 Int. Cl. B01k 3/100 US. Cl. 204-275 6 Claims ABSTRACT OF THE DISCLOSURE A process for partial electroplating using a plating head carrying the anode and which is traversed by the electrolyte is characterized by the fact that it proceeds continuously withthe exclusion of air or oxygen. The electrolyte is supplied from an electrolyte tank by means of a pump unit through a hose system to the plating head which is pressed against the article to be plated so that the article therefore acts as a cathode. The ends of the hose system for the head are immersed in tanks which may be filled for example, with cleaning liquid or an etchant and may be thereafter connected with gas tanks and the electrolyte as desired. The apparatus includes hose pumps comprising rotating members which cyclically operate upon a portion of the hoses connected to the electrolyte or the fluid for the purpose of directing the electrolyte or fluid from a tank source up to the electroplating head. The head is held against the article for example, a boiler which is to be electroplated with the interposition of a sealing material. Within the plating head the direction of flow of the electrolyte is opposed to that of the electrical current and the anode is located behind the cathode in respect to the flow direction, precious metal electrode which' is insoluble in the electrolyte may also be used so that the material to be deposited is then taken only from the electrolyte.

SUMMARY OF THE INVENTION This invention relates in general to a process and apparatus for electroplating and in particular, to a new and useful process for electroplating in which a plating head is moved along or into engagement with the article to be partially electroplated and that it is applied with the exclusion of air or oxygen and is supplied by electrolyte from one or more electrolyte tanks which is pumped through a house system.

In carrying out electroplating processes it is customary to fix the apparatus and the object to be plated in a stationary manner, the object being immersed in vessels filled with electrolyte. The size of the vessel limits the dimensions of the workpieces. In order to remedy this it is a known practice to use a gun type plating head where the electrolyte is drawn or forced to the workpiece to be partially plated by means of a water jet pump. The disadvantages of this arrangement is the requirement for continuous replenishment of the electrolyte liquid. Due to this as well as due to the use of a suction medium for example, air, only coatings of small film thicknesses can be applied and these coatings usually adhere badly on the base material. An exact pretreatment of the surface to be plated is not possible with such systems. In addition, from the gaseous suction medium undesirable chemical reactions are produced and hence contamination of the unused electrolyte are to be expected.

Similar disadvantages result from an arrangement where a partial electroplating is proposed but with a recapture of the electrolyte which is passed along the cathode. The two tanks used for this operation, namely the inflow and the outflow tank, are brought directly to the workpiece and movement of the electrolyte occurs by gravity. It is very costly to arrange the electrolyte tanks directly at the workpieces and the apparatus for carrying such tanks must be built to be very steady. The dimensional ratio of the portable portion of this electroplating unit to that of the desired partial electroplating area at the workpiece is so unfavorable that exactly defined or narrowly delimited electroplating adapted to the particular conditions appears to be almost impossible.

The known arrangement mentioned above as well as the others known in the prior art have still further disadvantages. The pretreatment of the parts to be electroplated in stationary vessels which are to be treated by additional special pretreatment methods always cause contact only for a short time with the surrounding air and the dust particles which may be contained therein so that a good bonding is jeopardized at least locally. In addition, in most methods the keeping of the electrolyte baths clean raises considerable problems. There is always a likelihood of the fouling of the electrolyte by precipitating an anodic mud, by contaminations from the air, by abrasion of mechanically moved parts inside and outside of the bath and many other operating difficulties so that there is an adulteration of the electrolyte composition. This also occurs in any event, the dillution of the bath by the use of rinse water as well as by the use of residual liquids of preceding baths adhering to the workpieces.

It is an object of the invention to avoid the disadvantages of the prior art by providing a process for partial electroplating by means of a plating head which carries the anode and which is traversed by an electrolyte and wherein the process can be carried out with the exclusion of air or oxygen. In a preferred embodiment of the invention the electrolyte is supplied from an electrolytic tank which may be arranged at a stationary location and through a hose system including a pump operating on a section of the hose to effect the transmission of the electrolyte therethrough. The ends of the hose are immersed in a selected one of various tanks including the electrolyte tank as well as cleaning liquid tanks and inert gas tanks and they are easily positionable to be connected to the pumping arrangements to pump the associated fluids therethrough to the electroplating head. The apparatus of the invention advantageously includes pumping elements which may be associated with one or more hoses of a hose system and made operable upon the hose to force liquid therethrough, and the ends of the hoses may be arranged within either a gas tank, an electrolyte tank or one or more tanks with cleaning liquids therein. The systems advantageously include one or more suction hoses which may have associated valving to permit them to be selectively turned on or turned off.

By the process of the invention, it is possible to provide for the preparation of the workpiece surface to be plated as well as for subsequent electroplating in accordance with which type of liquid is directed up to the electroplating head. The electroplating head itself may be applied without interruption and with the exclusion of air in a self-closed system to the workpiece so that contamination of the baths with one another or with the outside atmosphere is avoided. In this manner an optimum electrolyte movement is achieved and by an exact design of the construction of the plating head in accordance with the invention adaptation to the particular requirements of each case is rendered possible in a similar manner.

Thus not only are the disadvantages which occur in the known process avoided, but satisfactory deposition electroplating process. The bonding strength between the.

ground material and electroplated layer then in effect corresponds to that of the ground material and the electroplated layer itself becomes homogeneous.

Accordingly, it is an object of the invention to provide an improved process for electroplating which includes applying an electroplating head in engagement with the article to be electroplated and with a sealing therebetween, and delivering a preparation liquid to the electroplating head and subsequently an electrolyte while maintaining the exclusion of air. as the electroplating process is continuously carried out.

A further object of the invention is to provide a process and apparatus for electroplating wherein an electroplating head is moved or held in a position sealed against the article to'be electroplated and wherein the electroplating liquid is supplied to the head from one or more tank supplies; of either a cleaning or electrolyte solution or a gas, and wherein the solution is supplied through a hosevsystem which includes one or more suction end portions having valve means permitting them to be turned on or off and which may be oriented in an associated solution or gas, the hose means being associated with pump elements which efiect the pumping of the liquids therethrough when the valve means are opened.

A further object of the invention is to provide an electroplating device which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there are illustrated a preferred embodiment of the invention.

BRIEF. DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a diagrammatic partial elevational and partial sectional view of an apparatus for electroplating in accordance with the method of the invention; and

FIG. 2..is an enlarged transverse sectional view of another embodiment of plating head construction in accordance with the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings in particular, the invention embodied therein in FIG. 1 comprises" an electroplating system for repairing a defective area for example, on a copper boiler or kettle 15. For this purpose, a plating head 1 designed in accordance with the invention is pressed against a workpiece such as a copper boiler 15 and provides a sealing engagement therewith. The boiler 15 acts,

as a cathode. (similar to workpiece cathode 21 as shown in FIG. 2) in the area of its defects permitting the fiow of the material of electroplating in the direction of the arrow 22. The transition from the plating headl to the boiler 15 is advantageously closed off from the outside by packing materials, so that access or air can be avoided with certainty.

In accordance with the invention, the plating head 1 is connected with a hose system generally designated 4 which includes. a delivery portion 4a which is connected to the head lat one end and has an opposite end connected to a bifurcated valve connection 50 having

valves

5 and 6 which may be set for flow of liquid therethrough (the valve 5 or to prevent liquid flow therethrough as (the valve 6). Each valve fitting 5 and 6 is connected with a further hose portion 4b and 4c having

suction ends

9 and 7 which may be oriented as desired in one or more of a plurality of electrolytic tank supplies 2 to a gas bottle 14, or to one or more treatment liquid supply

liquid tanks

11 or 12. The treatment liquid in the tank 11 may comprise, for example, distilled water and, the liquid in the tank 12 may comprise an etchant or other liquid which is particularly necessary for the process step. The hose system 4 also includes a hose return conduit 4d which is indicated in the drawing as being immersed in a tank 18 which is provided, for example, for the return of the electrolyte liquid back to the electrolyte tank 2. The return tank 18 is separated from the outlet or supply tank portion 17 by a filter 19 in order to ensure that there is no contamination of the electrolyte and that any conreturn fluid delivered to the tank 18 is directed through the filter 19 before it is withdrawn for delivery to the head 1.

One or more of the suction ends 9' or 7 may be inserted into the suction tank portion 17 of the electrolyte tank 2 and in accordance with which one is so inserted, the pumps 3a and 3b are actuated. In theshowing of FIG. 1, the pump 3b is not operating and the valve 6 is'closed so that electrolyte moves upwardly from the suction end .9 through the tube 4b to the tube 4a and to the head 1 and to workpiece 15. Return electrolyte is circulated in a direction of the arrow 23 and downwardly in the tube 4d to the return portion 18 of the electrolyte tank 2.

Before the electrolyte is directed to the head 1 however, in most instances, it is preferable to first circulate a preparation liquid such as an etchant from the tank 12 and this is accomplished by inserting the suction end 9 of the tube 4b into the tank 12 which contains the etchant material. At approximately the same time and with the valve 6 closed the tube end 7 of the tube portion 40 is inserted into the tank 11 which is filled with a distilled water.

After adequate precleaning of the part 15 at the location which is to he electroplated by the etching material of tank 12, the valve 6 is opened also and distilled water is drawn into the hose system 4. Shortly thereafter the valve can be closed to cut off the supply of the etchant material from the tank 12 andthis makes the change over to distilleclwater from the tank 11 possible without causing the system to draw in air or other undesirable gases. With such an arrangement it is also possible to arrange other materials in the

tanks

11 and 12 or other tanks which would make it possible to provide for electrolytic degreasing for example.

The next process step is caried out by directing the suc tion end 9 of the tube 4b into the electrolytic tank 2 and the valve 5 is opened and, after filling the respective part of the hose system with the electrolyte, the valve 6 is closed. The process of electroplating can start for which purpose the cathode which is the copper boiler 15 and the anode which is present in the plating head 1 are connected with the current source 16 simultaneously.

The discharge of the liquid flushed through the plating head 1 occurs according to the direction of the arrow 23 from the end 8 of the hose system 4. The end 8 may be directed into the atmosphere so that the liquid is lost, or, it may be immersed in the tank 17 together with the

hose end

7 and 9 or into a separate tank 18 which is separated by the filter 19 from the tank 17. With the division of the tank by the filter 19' the electrolyte liquid is directed from the head 1 to the tank 18 through the filter 19 into the tank 17 from which it may be picked up again and circulated back to the head. In this manner the anodic mud etc., which is obtained upon issuance from the plating head 1 is retained in the inlet tank 18 and the part of the electrolyte which enters the plating head remains clean.

Should it be necessary, especially during a long lasting electroplating process, to replenish the electrolyte an additional tank (not shown) may be provided and the switching effect may be carried out by directing one of the hose portions 4c into the new tank before the supply in the present tank is exhausted and then gradually admitting the new supply by the opening of the valve associated with the hose which has been directed into the new supply. The same is true also in respect to the use of any additional liquids for cleaning the areas to be plated as for example ammonium persulfate or dilute sulphuric acid may be directed to the head 1 in this manner. It is also possible to carry out the change of one liquid to the next with the insertion of a shielding gas which is contained in the bottle 14. In this case, of course, the respective part of the pump unit 3 could be turned off, the pressure in the gas bottle 14 being sulficient to cause the liquid to flow to the head 1. In any case, there is achieved a change of bath without loss or dillution of the bath liquid and the surface of the workpiece is protected by a shielding gas during the changeover. Such a gas shielding process will be applied especially when electroplating easily oxidizible metals as for example, molybdenum, titanium, and steel.

In a further development of the invention, it is proposed to provide an electroplating head generally designated 1' as shown in FIG. 2 which is constructed so that the flow of electrolyte is opposed to that of the electrocurrent and for this purpose, the anode 20 and the workpiece forms a cathode 21 are oriented to produce this condition (for example as disclosed and described in co-pending application Ser. No. 873,165, filed on Nov. 3, 1969). This is achieved so that the anodic mud which always forms when using the filter 19 as shown in FIG. 1, cannot deposit on the cathode. Such material would now form only behind the cathode and would be floated away in the direction of flow of the electrolyte. With the plating head 1, as shown in FIG. 2, the electrolyte enters in the direction of the arrow 24 and moves through a tubule or conduit 25 and flows through the cathode 21 through bores 26. The plating head 1' which is circular in top plan view is provided with a electroplated collar 27 which is formed, as indicated in FIG. 2, at a spaced location from the anode 20 which is located behind the collar 27 in respect to the direction of flow and is connected with the current source through a junction or terminal 28. The issuance of the electrolyte occurs in a direction of the arrow 29 through the tubule or conduit 30.

As shown in FIG. 2, the cathode workpiece 21 15 connected to a capillary tube 3' which is threaded through the electroplating head and into the workpiece 21. In electroplating, an electroplating collar 27 is generated which joins the workpiece 21 to the tube 3 with a strength Sll'Illlar to that of a weld but without causing the disadvantages arising from a heating method of joining. The electrolyte flows from the inlet tube 25 in a direction of the arrow 24, and into an annular space 13 within the head, which connects through openings 26 to an annular space 14, which is located above the collar 27 and around a cylindrical portion of the head which encompasses and insulates the tube 3'. The electrolyte first washes the cathode and then flows upwardly in the space 14 through the annular gap to wash the anode and move outwardly through the outlet 30.

The arrangement of the invention is such that the fiow of the electrolyte from the inlet 25 to the outlet 30 is such that it is opposite to the direction of electrical current flow from the anode 20 to the

cathode

27, 21. The flow condition prevents any sediment formation on the cathode by locating the anode downstream in respect to the electrolyte flow so that the electrolyte will wash over the.

cathode and prevent any deposition of mud thereon.

Because of the electroplated collar 27 the two telescoped tubules acting as a cathode 21 are in the present example connected together with a strength which is similar to a welding of the two parts without causing the disadvantages occurring due to the otherwise necessary heating.

In another development of the invention a precious metal electrode which is insoluble in the electrolyte for example, platinum is provided so that the material to be deposited will be taken along only from the electrolyte and the electrode need not be replenished in any manner. Thereby the danger of mud deposition on the workpiece is eliminated and the electrode can be adapted to any desired workpiece form and thus a correspondingly defined electroplating can be formed in a uniform coating as the result.

What is claimed is:

1. A device for electroplating, comprising an electroplating head having a cathode portion adapted to be connected to a workpiece and an anode portion, means for establishing an electrical potential between said cathode portion and said anode portion of said head, said head having an inlet fitting and an outlet fitting spaced from said inlet fitting and an interior flow passage from said inlet fitting past said cathode portion and said anode portion to said outlet fitting and hose means connected between said inlet and outlet fittings for continuously and selectively alternately circulating a treatment liquid and an electrolyte to said head and for excluding air from said cathode portion and the workpiece when changing from circulating treatment liquid to circulating electrolyte and vice versa.

2. A device according to claim 1, wherein said hose means includes a first main conduit, a first branch conduit and a second branch conduit, and pumping means associated with said first and second branch conduits for pumping liquid through said branch conduits to said main conduit, said first and second branch conduits being adapted to be positioned in an electrolyte and/or a treatment liquid.

3. A device, according to claim 2, including valve means between first and second branch conduits and said main conduits for selectively connecting and disconnecting said branch conduits to said main conduit.

4. A device, according to claim 3, including a separate pump associated with each of said branch conduits, said branch conduits comprising hose members, said pumps comprising a member defining a receiving groove for a hose member and a rotatable member engageable with the hose for forcing liquid therethrough as the member is moved in engagement with said hose.

5. A device, according to claim 4, including an electrolytic tank, and a return conduit extending from said head back to said electrolyte tank.

6. A device, according to claim 5, wherein said electrolyte tank is divided by a filter, said return conduit being in said tank on one side of said filter, one of said branch conduits being in said tank on the opposite side of said filter whereby electrolyte which is returned by said return conduit flows through said filter and upwardly through said one of said branch conduits to said main conduit.

References Cited FOREIGN PATENTS 1912 Great Britain 204--224 OTHER REFERENCES WINSTON A. DOUGLAS, Primary Examiner M. I. ANDREWS, Assistant Examiner