US3436330A - Electroplating apparatus - Google Patents

Description

April 1, 1969 wRlGHT ET AL ELECTROPLATING APPARATUS Sheet Filed July 15, 1965 li ove 21 550 r MAL 02 WE/Gf/ 7' JAIL/5 w. HEWLY 3 1 7w flity.

April 1, 1969 M. wmsm" ET AL ELECTROPLATING APPARATUS M H m 5 o a 3 w .t I? m M 5 xi Ad M April 1, 1969 M. WRIGHT ET ELECTROPLATING APPARATUS Sheet of 4 Filed July 15. 1965 Invenior. MALOE VE/6H7 JAMf'j V HEALY April 1, 1969 w i ET AL ELECTROPLATING APPARATUS Sheet Filed July 15, 1965 Inventor M4402 WEIGHT JAMES W. HEAL) by w M.

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United States Patent 3,436,330 ELECTROPLATING APPARATUS Malor Wright, Lexington, and James W. Healy, Wakefield,

Mass., assignors to United-Carr Incorporated, Cambridge, Mass, a corporation of Delaware Filed July 15, 1965, Ser. No. 472,095 Int. Cl. C23b 5/68 US. Cl. 204207 6 Claims ABSTRACT OF THE DISCLOSURE An electroplating apparatus for a continuous wire comprising supply means, guide means, reagent tubes, electroless plating means and electrolytic plating means, said reagent tubes being orientated angularly in relationships to the horizontal Wire, and said wire being treated in the reagent tubes and then electroless plated without contacting any surface.

This invention relates generally to plating methods and more specifically to methods of plating the outer conductor on a coaxial cable.

An object of the present invention is to provide an apparatus for continuously plating a substrate.

Another object of the present invention is to provide an apparatus for continuously plating a cylindrical substrate.

In the drawings:

FIG. la is a side elevation, partly in section, of the reduction module of the cable plating line;

FIG. 1b is a side elevation, partly in section, of the plating module;

FIG. 10 is a side elevation of the take-up module;

FIG. 2 is an enlarged view of the reagent tubes, partly in section;

FIG. 3 is an enlarged sectional view of the electroless copper plating station; and

FIG. 4 is a front elevation partially broken away and partially in section of a single drive roller, the frame supporting same and the main drive shaft.

Heretofore the preparation of core strands for electroplating in a continuous process was very difficult, particularly if long lengths of the core strand were required. As the core strands were transferred in coils from bath to bath, separate strands of the coil would either rub one another or contact the sides of the container producing bare spots. It was therefore highly desirable to develop a method of handling the core strands. The idea of dripping the solutions on the cable as it passed proved to be a spotty and highly inadequate approach. The use of water-wetted glass tubing to accomplish the required result was then thought of and has proved successful.

In the drawings there is shown an apparatus for plating a high frequency coaxial cable core 12. The cable core 12 comprises an inner conductor coated with a jacket of dielectric such as polyethylene or Teflon. The jacket may, if required, be externally grooved.

The apparatus comprises three modules, a reduction module, a plating module and a take-up module. Before the strand or strands of coaxial cable core enter the reduction module, it has already gone through certain preplating operations which would include a cleaning with alkaline or other types of cleaning solvents and also a pre-plate acid etch.

The strand of the coaxial cable core 12 is wound on a supply drum 14 which is immersed in a container 10 filled with a heated solution of clean, hot, deaerated water with a small amount of potassium dichromate. The strand of the coaxial cable core 12 is then'brought into the plating line which includes the reduction module, the plating module, and a take-up module. The strand of "ice coaxial cable core 12 is stretched from the supply drum 14 over a guide roller 16 through a series of reagent tubes 18 to the plating guide roller 20. From the point where the strand 12 passes over the guide roller 16 until it reaches the plating guide roller 20, it only passes through the necessary reagent solutions or through air without touching any other physical surfaces.

Each of the tubes 18 comprises a single treating station in the reduction module. The necessary reagents are fed into pipes down into the reagent tubes 18 from chemical dispensing tanks (not shown) by gravity feed or other feed means.

At the first station, the coaxial cable core strand 12 undergoes a second etching procedure to insure that the surface is hydrophilic. The flow rate is adjusted to provide a complete change of solution in the tube 18 approximately every 2.5 minutes. This adjustment is accomplished by using a clamping means or a metering device on the plastic hose leading from the dispensing tank to the supply nozzle of the tube 18.

The next station is a rinse station which utilizes deionized water.

Station 3 provides a sensitizing treatment of a readily oxidized material, in this case stannous chloride, at room temperature, the flow rate being adjusted for complete changeover every four minutes.

Station 4 is another rinse adjusted to provide a flow rate providing a complete change every 2.5 minutes.

Station 5 deposits a catalytic film on the cable core. The catalyst in this case being palladium chloride. Silver compounds may also be used in place of the palladium.

Stations 6 and 7 are rinses.

Station 8 exposes the coaxial cable core to an electroless copper solution containing an A solution having a combination of copper sulfate and formaldehyde and a B solution of sodium carbonate, sodium hydroxide and Rochelle salt. The A and B solutions are stored in separate containers and are mixed just prior to use.

Each of the reagent tubes 18 has an extension or supply nozzle 19 on its upper surface which engages with the hose from the chemical dispensing tanks and since each of the reagent tubes 18 is water wetted, surface tension will maintain a full tube of the reagent solution. Therefore, the strand of the coaxial cable 12 passes through what may be termed cylinders of reagent separated by air spaces. If no reagent is added to the reagent tube 18, the reagent in the tube 18 will remain stationary. A runofl? tank 24 surrounds the reduction module on three sides so that the dripping from the tubes 18 is caught in the runoff tan-k 24. Each of the reagent tubes 18 is tilted slightly at the portion closest to the supply drum 14 and the reagents dripped into the tubes 18 are introduced in a counter current fashion so that the fresh portion of the solution is directly under the extension and by the time the reagent reaches the end of the tube for runoff, the useable chemicals have been exhausted for the purpose intended. The strand 12 moves in a direction counter to the flow of reagent in the reagent tube 1 8. A set forth hereinbefore, the last station in the reduction module is the application of an electroless copper plate in preparation for the final electroplating. In this case the electroless plating tube 21 of the electroless plating station is split along its top surface to allow gases to escape. The plating solutions are fed through a nozzle having a T shape so that the A and B solutions are mixed just prior to entry into the main body of the tube 21. The electroless plating tube 21 is also tilted in the same manner as the reagent tubes 18. The electroless plating station is equipped with strip heaters and a thermistor temperature control the strand 12 then enters the electrolytic plating module.

The plating module starts with the plating guide roller 20 which guides the coaxial cable core 12 onto the first plating or drive roller 22. The drive rollers 22 are twelve in number, are in spaced parallel relation to each other, and are placed transversely in relation to the strand 12. Each of the drive rollers 22 has a series of guide grooves 25 formed around the periphery in sets of three, for a purpose to be described hereinafter, and a pair of drip grooves 26 spaced from each end of the plating rollers 22. The drip grooves 26 are formed to prevent solutions from escaping along the shaft 28 of the drive roller 22 since these solutions may corrode the worm gears (not shown) which rotate the drive rollers 22. Depending on the length of the drive rollers 22, a number of parallel strands of coaxial cable core 12 may be simultaneously treated by adding the required number of sets of guide grooves 25. The reason that three grooves are provided in each set of guide grooves 25 is that Wear takes place at these grooves and, therefore, three potential areas of wear are provided to avoid the necessity of replacing a plating roller 22 when one area of wear has appeared.

As shown in FIG. 1b there are twelve plating or drive rollers 22 whose axes are in parallel relationship with each other; all of which are driven by a separate worm gear mechanism associated with each roller and all mounted on a frame 30 which is mounted outside and inside the plating tank 32 and moveable with the plating tank 32 set down below the surface of the drive rollers 22 and in which are set a series of subsidiary or idler rollers. The drive rollers 22 are all driven by a common drive shaft 36 (shown in FIG. 4) connected to the mentioned individual worm gears. The diameter of each of the drive rollers 22, in sequence, is slightly larger than the one before, to slightly stretch the strand 12 and thereby keep the strand 12 from jumping from the guide groove 25. For the sake of clarity the first of the idler rollers will be referred to as a primary idler roller 34a and the second and third will be, hereinafter, referred to as secondary idler rollers 34b with the remaining rollers being referred to as tertiary idler rollers 34. The primary idler roller 34a is set approximately /3 the way down from the top of the plating tank 32 and the secondary rollers 34b are each set approximately down from the top of the plating tank 32. Tht tertiary idler rollers 34 are set approximately /3 down from the top of the plating tank 32 as shown in FIG. lb. Each of the idler rollers 34 is similar to the drive rollers 22 except they do not have the drip grooves 26 and they are formed of a corrosive resistant material and need not be electrically conductive as are the drive rollers 22.

Voltages are impressed on the drive rollers 22, the first drive roller having a voltage of approximately 15 volts, the second drive roller having a voltage of 10 volts, the third drive roller having a voltage of volts and the remaining drive rollers having a voltage of approximately 2 volts. This variation in voltage is provided to overcome the very high skin resistance of the plate on the strand 12 at the early stages of the electrolytic plating operation. As the plate is thickened, the necessity for the high potential is reduced and therefore, the voltage is reduced accordingly. The length of the strand being plated between the first drive roller 22 and the primary idler roller 34a is of a predetermined length providing an efficient plating operation. The length of the strand 12 between the second drive roller 22 and the first secondary idler roller 34b is of a greater length than that between the first drive roller 22 and the primary idler roller 3411, which length is maintained between the third drive roller 22 and the second secondary idler roller 34b. The length between the fourth drive roller 22 and the first idler roller 34 is greater than that between the second drive roller 22 and the first secondary idler roller 34!), which length is maintained for the remaining plating operation.

The impressed voltages are higher in the beginning of the plating operation because of the higher resistance of the thin skin of the plated metal and path lengths are reduced because the amount of current which can be carried by the developing outer conductor and the plating rate can be held constant by varying the strand length in the initial stages. By the time the fourth drive roller has been passed the electrical resistance of the plating solution controls the plating rate. These procedures provide that the deposition of the plate will be at a nearly constant rate.

The strand 12 is passed over the first plating guide roller 20 down under the primary idler roller 34 and this sequence is continued throughout the length of the plating line. A series of anodes 38 are suspended below each drive roller 22 and fixed in position by passing each anode 38 between a pair of parallel bars 40 connected to the frame 30 in spaced parallel relation to the drive rollers 22, as shown in FIG. 1b. The solution in the plating tank 32 is CuSO and H 50 The deposition of the copper plate on the strand 12 is brought about by processes well known in the art.

At the completion of the plating operation the strand 12 is passed through a treatment station which includes a water rinse station 42 and an anti-tarnish station 44 which uses an amine rinse as a reagent and thence onto a take-up reel 46.

While there has been illustrated and described a preferred embodiment of the invention, it should be understood that the invention is best described by the following claims.

What is claimed:

1. An apparatus for plating a strand, said apparatus comprising a supply means, a guide means, a series of sloping reagent tubes, an electroless plating means, and an electrolytic plating means, said reagent tubes being in an in-line relationship longitudinally, and each of said reagent tubes having a forward terminal end and a rear terminal end, said forward terminal end being on a plane above the plane of said rear terminal end, and each of said reagent tubes having a means of receiving reagents proximate said forward end, whereby the strand passes from said supply means over said guide means horizontally through said reagent tubes and said electorless plating means to said electrolytic plating means and from said guide means to said electrolytic plating means, the strand touching only reagents and air.

2. An apparatus for plating a strand as set forth in claim 1 wherein each of said reagent tubes has a supply nozzle extending therefrom to engage a reagent supply hose.

3. An apparatus for plating a strand as set forth in claim 2 wherein said guide means comprises a roller and said electrolytic plating means has a plating guide roller and the strand touches only reagents and air from said guide roller to said plating guide roller.

4. An apparatus for plating a strand, said apparatus comprising a supply means, a guide means, a series of sloping reagent tubes, a strand to be plated, an electroless plating means and an electrolytic plating means, said reagent tubes being in an in-line relationship longitudinally, and each of said reagent tubes having a forward terminal end and a rear terminal end, said forward terminal end being on a plane above the plane of said rear terminal end, and each of said reagent tubes having a means of receiving reagents proximate said forward end, and reagents added at each reagent tube, sand strand moving horizontally through said reagent tubes in one direction and the reagents flowing through said reagent tubes in the opposite direction toward said rear terminal ends whereby the strand passes from said supply means over said guide means through said reagent tubes and said electroless plating means to said electrolytic plating means and from said guide means to said electrolytic plating means, the strand touching only reagents and air.

5. An apparatus for plating a strand of material, said apparatus comprising a reduction module, an electroplating module, and a take-up module, said reduction module including a supply means, an apparatus for plating a strand, said apparatus comprising a supply means, a guide means, a series of sloping reagent tubes, an electroless plating means, and an electrolytic plating means, said reagent tubes being in an in-line relationship longitudinally, and each of said reagent tubes having a forward terminal end and a rear terminal end, said forward terminal end being on a plane above the plane of said rear terminal end, and each of said reagent tubes having a means of receiving reagents proximate said forward end, Whereby the strand passes from said supply means over said guide means horizontally through said reagent tubes and said electroless plating means to said electrolytic plating means and from said guide means to said electrolytic plating means, the strand touching only reagents and air and said electroplating module comprising an electroplating apparatus comprising at least two drive rollers, an idler roller, and anode means, a frame and a tank means, said idler roller set below the axis of said drive rollers in said tank means, the first of said drive rollers having an electrical potential greater than the other of said drive rollers when said apparatus is in operation, said drive means engaged to said frame above said tank means and said anode means mounted on said frame within said tank means spaced from said drive rollers and said idler roller.

6. An apparatus for plating a strand, said apparatus comprising a supply means, a guide means, a series of reagent tubes, an electroless plating means, and an electrolytic plating means, said reagent tubes being in an inline spaced relationship longitudinally, and each of said reagent tubes having a forward terminal end and a rear terminal end, each of said reagent tubes having a means of receiving different reagents and said reagent tubes being spaced from each other and the path of said strand being horizontal and in angular relation to the horizontal axis of said reagent tubes, whereby the strand passes from said supply means over said guide means through said rwgent tubes and said electroless plating means to said electrolytic plating means and from said guide means to said electrolytic plating means, the strand touching only reagents and air.

References Cited UNITED STATES PATENTS 1,065,090 6/1913 Werth 2O4-237 XR 1,322,494 11/ 1919 Merritt 204-28 1,454,224 5/ 1923 Schmidt.

1,862,138 6/1932 Elsey 204-28 2,141,3'82 12/193 8 Perm.

2,392,687 1/ 1946 Nachtman 204206 2,445,675 7/1948 Lang 204209 3,261,771 7/1966 Polleys et al 20428 FOREIGN PATENTS 573,983 12/1945 Great Britain.

1. H. MACK, Primary Examiner.

W. VAN SISE, Assistant Examiner.

US. Cl. X.R.

204-28; ll8429; 13412Z

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