CA1203505A - Apparatus and method of treating tabs of printed circuit boards and the like - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Printed circuit boards are carried generally vertically, along a path, with the tabs at the lower end being immersed in an electrolyte. The boards are automatically conveyed through opposed serially arranged pairs of rollers, which drive them along their path. Brushes wipe the boards to prevent contact with electrolyte above the desired contact level, as they are conveyed along the path. The solution is constantly replenished and turbulence pro-vided by delivering electrolyte solution, with insoluble metallic ions in it, by pumping the solution from a sump, through an array of nozzles along each side of the path, thus providing fresh electrolyte along with providing tur-bulence to the electrolyte. The nozzles are charged at a sufficiently low level to avoid their destruction. Electrical contact is made with the printed circuit boards, by means of serially engaging the boards with spring fingers of a continuous conductor along each side of the boards as they are conveyed along their path, and thereby conducting the applied charge to the immersed tabs, whereby the tabs function as cathodes for electrodeposition of metallic ions thereon. The drive for the boards is provided by means of opposed pairs of rollers. One roller in each pair is a driving roller, with the opposing roller functioning as an idler, but forming an interference fit between the rollers as the boards are carried therebetween. The idler rollers are arranged in a bank, for adjustably being positioned to accommodate boards of various thick-nesses. The electrical connection with the upper ends of the boards may like-wise be adjustably positionable to accommodate boards of various heights.

Description

~203505 This is a divisional of copending Canadian patent application Serial No. 412,693 filed on October 1, 1982 in the name of Chemcut ~orporation.
In the art of printed circuit board manufacture, it is known to plate tabs of the boards with various substances, particularly gold, and generally after first nickel plating prior to gold striking and plating, for the purpos-e of obtaining better resistivity, high conductivity at the connection points defined in the tabs, and high corrosion resistance. Such techniques have frequently experienced problems in driving the printed circuit boards positively along their path, and in satisfactorily applying the electro-lyte to the tabs, in sufficient density, during the residence time of the tabs in the solution.
Accordingly, it is a primary object of this invention to provide a novel electroplating apparatus and method, for electroplating tabs of printed circuit boards in which the above noted drawbacks are obviated or mitigated.
rt is a further object of this invention to accomplish the above object, wherein the electroplating of the tabs, involves the electrodeposition of gold onto the tabs.
It is another object of this invention to accomplish the methods established by the apparatus discussed above.
It is another object of this invention, to provide for adjustability with respect to the drive of boards through their paths, whereby boards of different thicknesses may be accommodated.
It is a further object of this invention to make electrical contact with printed circuit boards, at their upper ends, outside of contact with the electrolyte, but to provide for adjustability of such contact, in order to accommodate boards of various heights.

, i~

It is another object of this invention to deliver printed circuit boards along their paths through treatmen~ stations.
It is another object of this invention to accomplish the above objects, wherein the boards are appropriately guided during their movement along the path.
It is another object of this invention to accomplish the above objects, wherein the boards are moved through the apparatus by means of opposed rollers, allowing for resilient sandwiched engagement of the boards therebetween, as the boards move along their path.
According to one aspect of the present invention, there is provided apparatus for localized treatment of tabs of printed circuit boards and the like comprising: means deining a treatment zone; conveying means for conveying the tabs of printed circuit boards on lower ends thereof, through the treatment zone, with the boards in generally upright disposition along a predetermined generally vertical path; delivery means for delivering a treatment fluid to boards in the treatment zone; with said conveying means comprising a plurality of opposed roller pairs along said path outside of said treatment zone, with one roller of each said pair being mounted on each side of said path, for board engagement therebetween; and with the opposed rollers of each said pair having resilient board-engaging surfaces and are mounted for rotation relative to each other to be in interference fit with a board upon receiving a board therebetween.
According to another aspect of the present invention, there is provided apparatus for localized electroplating of tabs of printed circuit boards and the like, comprising: means defining a bath zone of electrolyte;
conveying means for conveying printed circuit boards such that tabs on lower ~035QS

ends thereof are carried through the bath zone, with the boards in generally upright disposition along a predetermined generally vertical path; delivery means for delivering a sufficient flow of electrolyte to the bath zone, to maintain a bath depth of a predetermined desired level; means automatically and serially engaging portions of the boards that are out of the solution and making continuous electrical contact therewith as the boards are conveyed through the solution, whereby the immersed board tabs function as electrodes;
wherein said conveying means comprises a plurality of opposed roller pairs along said path outside of said bath zone, with one roller of each said pair being mounted on each side of the path, for board engagement therebetween;
wherein the rollers in each said pair are in resilient biased-together engagement for resiliently engaging boards in sandwiched relation therebetween.
According to a further aspect of the present invention, there is provided the method of localized electroplating of tabs of printed circuit boards and the like, comprising the steps of: providing a bath zone of electrolyte; conveying printed circuit boards through the bath, in generally upright disposition, along a predetermined generally vertical path, with the tabs being carried through the bath; delivering a sufficient flow of electrolyte to maintain a bath depth of a predetermined desired level;
automatically and serially engagi.ng portions of the boards and making electrical contact therewith out of the level of the bath, as the boards are carried through the bath, thereby making the board tabs function as electrodes in the electrolyte bath; wherein said conveying step includes engaging the boards serially between opposed pairs of rollers, one of which is a drive roller and the other a slideable idler roller, and applying continuous resilient force to the idler rollers to urge them toward their associated drive rollers.

1~03S05 The invention will now be described in greater detail with reference to the accompanying drawings, in which:
Figure 1 is a vertical sectional view, taken longitudinally through the apparatus of this invention, generally along the line I-I of Figure 2, and wherein a number of printed circuit boards are shown, being conveyed from right to left as viewed in Figure 1, with the tabs at the lower ends of the boards at a level for i.mmersion in the electrolyte bath, and with the illustration in Figure 1, being broken, to shorten the same long-itudinally as a drafting expedient.
Figure 2 is a transverse vertical sectional view, of the apparatus of Figure 1, taken ~enerally along the line II-II of Figure 1, wherein the board drive wheels, the noæzles, and the electrical contact means for the board, together with their adjustment, are all clearly illustrated.
Figure 3 is an enlarged fragmentary plane view of the drive apparatus, for driving the boards through their predetermined paths, and is taken generally along the line III-III of Figure 2, with portions being illustrated in section.
Figure 4 is an enlarged fragmentary horizontal sectional view, with portions broken away for the sake of clarity, taken through the board-engaging conductors and their conducting spring ingers, with the view of Figure 4 being taken generally along the line of IV-IV of Figure 2.
Figure 5 is an enlarged fragmentary horizontal sectional view, taken thxough the apparatus of this invention, generally on line V-V of Figure

2, and wherein the drive and idler wheels are illustrated for moving the board along its path, with the bank of idlex wheels having means for adjustably posltioning the wheels.
Figure 6 is an enlarged fragmentary horizontal sectional view, taken through the board as it is being conveyed along its path through the electrolyte and with an array of nozzles being illustrated, in section, along each side of the board path.
Figure 7 is an enlarged fragmentary view, similar to a portion of Figure 2, but wherein an alternative embodiment for the board drive through the apparatus is illustrated.
Figure 8 is a vertical sectional view, taken generally along the line VIII--VIII of Figure 7, and whexein the bladder means for applying a resi-lient counter-force for the drive rollers, is more clearly illustrated, and ,r lZ03505 broken away in the illustration to permit viewing of the slideable idler rollers.
Referring now to the drawings in detail, reference is first made to Figure 1, wherein the tab plating apparatus is generally designated by the numeral 20 as comprising left and right end walls 21 and 22, side walls 23 and 24, sump bottom 25, and top cover 26. Elongated vertical slots 27 and 28 are provided in walls 22 and 21, respectively, for accommodating ingress and egress of printed circuit boards 30, being received within the apparatus 20, and being delivered therefrom, in the direction of flow, along the predetermined path that will be apparent hereinafter, and as indicated by arrow 31 in Figure 1.
The electrolyte 32, is present in the sump defined by the walls 21 through 24, and sump bottom 25.
Electrolyte is pumped from the sump 32, by means of pumps (not shown) located in the sump 32, and delivered, up through delivery lines 33 and 34, located inside, but close to the walls 24 and 23, respectively, to respectively associated manifolds 35 and 36. A plurality of such lines 33 or 34, deliver electrolyte to the manifolds 35 and 36.
Elongated arrays of nozzle banks 37 and 38 extend horizontally be-tween inlet and outlet walls 22 and 21, as illustrated in Figures 1 and 2, each with nozzles 40 connected therewith and disposed along side the path of travel of the lower end of the printed circuit board 30 being delivered therepast, whereby electrolyte can be discharged through orifices 41 of the nozzles 40, to impinge upon both sides of the boards 30. The nozzle banks 37 and 38, are located in the bath 43, below the liquid level 44 thereof, and arc provided with electrolyte pumpcd under pressure, through suitable nipples 45, held in seated position in openings 46, by means of collars 47, in threadcd engagement with threaded members 48, that in turn are in threaded engagement with elbows 50, that communicate with the manifolds 35 or 36.

Electrolyte is therefore delivered from the sump 32, via lines 33, 34, via manifolds 35, 36, via elbows 50, via members ~8, via nipples 45, via nozzle banks 37, 38, and out through the orifices 41 of nozzles 40, while the nozzles 40 are immersed in electrolyte in the bath zone 43, below the level 44, and with the delivery of electrolyte through the nozzle orifices 41 serving to create a turbulence within the bath zone 43, for enhancing uniform distribu-tion of insoluble ions carried in acid solution, throughout the bath æone 43.
It will be noted that the rate of flow of the electrolyte into the bath zone 43, is at a sufficiently high level, to maintain the liquid level 44, 10 and thatoverflow ports 51, at the level 44, through walls 52 and 53 of the trough that forms the bath zone, enable return of electrolyte back into the sump 32, outside trough walls 52 and 53, for recirculation. Electrolyte re-turn holes 55 may also be provided in the bottom wall 56 of the trough 54, for facilitating greater flowthrough of electrolyte into the sump 32, and to in-crease the agitation provided by electrolyte flow in the bath zone 43.
It will be noted that a plurality of lower guide rollers 57 are ~otatingly carried on shafts 58, in an elongated groove 60, of a U-shaped track member 61, extending between the walls 22 and 21, and supported from the bottom 56 of the trough 54, by means of vertical standards 62. The rollers 57 function as idlers, and together with the upper inside portions of the upstand-ing legs 63, serve to guide the lower ends of the printed circuit boards30, as -they travel through the apparatus 20.
With particular reference to Figure 1, it will be apparent that a masked portion or stripe 65, is provided, spaced upwardly slightly from the lower ends of each of the printed circuit boards. The mask 65 may be an ad-hesively secured sheet, or may be a paint-like substance that has been applied, , where illustrated on the boards, across conductor portions of the boards,to de-fine a zone, below which plating is desired, but above which plating is not de-sired. Accordingly, the mask zone 65 serves to restrict the passage of electro-lyte to those portions of the boards 30 below the mask zones 65.
It will be noted that the nozzle orifices 41 are illustrated in Figùre 1 as being disposed at a level for plating of tab portions 66 of boards 30, as they are conveyed therepast.
At about the level of the mask zones 65 of the boards 30, it will be noted that longitudinally extensive wipers, 67 are provided. These wipers 67 are of the multiple filament brush type, constructed to be stiff, but yet to yieldingly engage opposite sides of the printed circuit boards 30 being conveyedtherepast, as illustrated in Figure 2, and above the level 44 of electrolyte or bath, to wipe from the boards 30, in vicinity of the mask zones 65, any elec-trolyte that may have been splashed onto, or otherwise come into contact with the boards 30 in the zones of mask 650 The wipers 67 extend generally longitudinally, between the walls 21 and 22, and are carried in suitable holders 68, of the transverse cross-section illustrated in Figure 2. The holders 68 are carried on opposite sides of the path of board flow, at the lower ends of upper bath zone covers 70 and 71.
Pairs o~ opposed drive wheels 72 and 73 are provided, along the path of flow of printed circuit boards, between the inlet and exit openings 27 and 28, respectively, with the rollers 72, 73 being on opposite sides of the path, and with the roller 73 being the idler roller in each instance, and with the roller 72 being the drive roller in each instance, and with the spacings between rollers 72 and 73 being set relative to the thickness of a given printed circuit board 3Q, such that, in each instance, there is an interference fit betweell the rollers 72 and 73 when a printed circuit board 30 is disposed between them. In this instance, only one of the rollers 72 or 73 in each pair, needs to be driven. It will also be noted that the rolling surfaces of the rollers 72 and 73, are pro-vided with a resilient nonconductive coating material, for assuring good grip with the printed circuit boards 30 during their conveyance throu~h the appara-tus 20.
The idler rollers 73 are carried in a suitable mounting block 74 of C-shaped cross section, by means of a shaft 74 extending between legs 76 and 77 of the mounting block 74. The block 74 has a plurality of slotted holes 77 therein, for receiving connector members 78 therethrough, with the lower ends of the connector members 78 being in threaded engagement at 80, in upper plate 70. It will be apparent that the mounting block 74 may be adjustably positioned,as desired, toward and away from the path of movement of printed circuit boards 30 between the rollers, such that the bank of rollers 73 may be moved closer to,or farther away from the rollers 72, by simple loosening of threaded members 78 and re-positioning-of the mounting block 74, as desired.
The drive rollers 72 are fixedly mounted, on drive shafts 82, lower ends of which are bushing-mounted at 83, in upper member 71, and with the shafts82 being driven, for positively rotating thc drive wheels 720 The upper ends of the shafts 82 have bevel gears 84 carried thereon, that in turn are in meshed engagement with bevel gears 85 carried on main drive shaft 86, that, in turn, is driven by a suitable motor 87.
~lorizontal support member 87, carried by wall 24, having bushings 88 thereir., supports the upper ends of the shafts 82, and gears 84 carried thereon, as well as supporting shaft supports 90 that, in turn, jo~rnal the main drive shaft 86.

_ 9 _ An upper guide track 92, is provided, constructed, so as, in trans-verse section, as viewed in Figure 2, to be of inverted U-shaped cross section.
The track 92 extends between inlet and outlet walls 22 and 21, respectively, of the apparatus 20, as illustrated in Figure 1, and as provided with depending legs 93 and 94, connected by web 95. At the upper end of the opening 96 in the track 92, there are provided a plurality of upper guide rollers 97, for engag-ing the upper ends 98 of the boards 30, and guiding boards 30 in their move-ment along the path through the apparatus.
The rollers 97 are of the idler type, mounted for rotation on shafts 100, with protruding shaft portions in engagement with opposite legs 93, 94, of the track member 92.
Below the guide wheels 97, in the track 96, Oll each sidc of the path of movement of the printed circuit boards 30 therebctween, there are providcd elongate continuous conductors 103, extending from one end wall 22 of the appar-atus, to the other 21. These conductors 103 are electrically connected, each by means of suitable lead lines 104, througll the track member 92, to conduct electricity to the upper ends of the printed circuit boards 30, through a plurality of serially disposed spring fingers 105, that are incompletely scvered from the conductors 103, and extend inwardly to engage opposite sides of the printed circuit boards 30, as the boards are delivered therepast, with the spring fingers 105 being in biased engagement with the oppositc sides of thc boards being delivered therebetween. The spring fingers 105 thus springingly engage the boards 30, and makc electrical connection with the upper ends of the boards, along their conductive portions. Thc conductive portions of the upper ends of the boards conventionally communicate with the tabs 66 at the lower ends of the boards, as printed circuit boards arc dosigned.

In order to accommodate printed circuit boards 30 of varying verti-cal heights, the track 92 that houses the guide rollers 97 and the elongate conductors 103 therein, is capable of being adjustably positionable at various heights. To this end the track member 92 is provided with a plurality of tapped holes 108 therein, along its length, for receiving, in threaded engagement therein, a plurality of threaded connectors 110. The threaded connectors are adapted to be slidingly positionable along vertical slotted holes 111, in track support 112, that~ in turn, is carried by upper wall 26. A sufficient number of track supports 112 are provided along the length of the track, to carry the same.
It will be apparent that the means for imparting electrical connec-tion to the upper ends of the printed circuit boards, as well as the means for guiding the upper ends of the printed circuit boards, are therefore all capable of being adjustably positioned vertically, without disturbing the drive for the drive rollers 72.
~ith particular reference to Figure 7, an alternative embodiment for the drive for the boards 30, is illustrated. In this embodiment, the opposed drive rollers 151 and 152 engage the boards 30 that are delivered serially therebetween, in much the same manner as the rollers 72 and 73 discussed above.
llowever, in this case, the rollers 152 are resiliently pressed against the boards 30, sucll that the rollers 151 and 152 sandwich the boards 30 therebetween.
Each roller 151 is mounted at its lower end with its shaft extension 153 car-ried in a bushing 154, with the bushing 154 being disposed in the blind hole 155, in lower mounting plate 156~ The lower mounting plate 156 is carried on horizontal frame member 157, by means of suitable bolts 158, or the like. The horizontal plate 157 is at about the same level as the horizontal plate 70 in the embodiment of Figure 2 discussed above, and the liquid level, nozzles, etc., 1203S0~

~yhile not sho~Yn in Figure 7, are similarly related to the plate 157, as to plate 7~ in the previous embodimen~O A separating plate 16~ is carried on support plate 156, and in turn carries an upper support plate 161 for the serially disposed rollers 151, mounted in a line, along one side of the vertical ~oard-receiving opening 1620 A portion of the shaft 163 at the upper end above the roller 151, is bushing mounted at 164, in plate 161, and plate 161 is secured to the spacer plate 160 by means of suitable fasteners 165. A bevel gear 166 is carried at the upper end of the rol~er shaft, above portion 163.
It will ~e apparent that each of the rollers 151 along the left side of the opening 162, is similarly mounted to that illustrated in Figure 7, and each is driven by means of a drive bevel gear 167 carried on a drive shaft 168, for rotation therewith. The drive shaft 168 is illustrated as being circular in cross-section, but could assume a rectan~ular or other cross-section, if desired.
At the right-most end of Figure 7, a plate 170 is provided, opposing plate 157, and in turn has an idler-bracket-supporting-plate 171 carried there-~bove, by means of suitable fastèners 1720 A plurality of recessed slideways 173 are provided in the plate 171, to provide for slideable mounting of slide-able idler roller mounts 174 therein, one in each slideway 173, for movement leftward or rightward as viewed in Figure 7 along the slideways 173, or into and QUt of the plane of the paper as viewed in Pi~ure 8. The mounts 17~ are pro-vided with upper and lower bores 175 and 176 to receive corresponding uppcr and lower ends of shaft portions carried by the idler rollers 153 therein, as ill-ustrated.
A spacer member 177 is carried at the right end of plate 171, and in turn, carries an upper plate 188, secured thereto by means of bolts 190, with the plate 188 providing an upper slide surface 191 for the upper surface 192 of the mount 174. The plates 171 and 18~ thus confine the slideable mounts 174, ~rom above and belol~, and the slideways 173 confine the slideable mounts to a sliding movement into and out of the plane of the paper as viewed in Figure 8.
An elongated bladder 193, of generally rectangular cylindrical cross-section in its free condition, is provided. The bladder 193 normally contains compressed air from a suitable source, and extends behind a plurality of mounts 174, generally along the length of the machine, from the inlet to outlet ends thereof, to provide a constant, but resilient force against the mounts 174, such that the idlers 152 carried b~ the mounts 174, are constantly urged into engagement toward the drive rollers 151, such that the boards 30 being conveyed between the rollers 151 and 152, are in resilient pressed engage-ment therebetweenO Any suitable source may provide the compressed air for the bladder 1~3~ It will be noted that, in Figure 7, the bladder 193 is illustrated to be somewhat flattened, indicating a compression of the same due to the pres-ence of the mounts 174. It will also be noted that the mounts 174, with their carried idlers 152,.are independently moveable as plates 130 progress through the machineO
It will be apparent that ~ipers 149, 179 like those 67 may likewise be provided, suitably carried in brackets 159, 169 at the lower ends of plates 157, 170, facing each other across opening 162~ Also, a suitable lower board support by means of rollers or the like, similar to those 57 as illustrated in Figure 2, may like~Yise be provided for supporting lower ends of boards 30, although the same is not specifically illustrated in Figure 7. Likewise, suitable upper support for the boards 30 may also be provided, similar to, or different than the adjustable vertically re-positionable roller guides illus-trated at the upper end of Figure 2~ All other working components of the _ 13 -apparatus, as illustrated in Figure 2, but which are absent from Figure 7, may likewise be provided, except to the extent inconsistent Witll the specific embodiment of Figure 7.
At the inner ends of the plates 161, 188, suitable conductors 195, 196, are carried, generally by means of threaded fasteners 197, 198. These conductors 195, 196 are elongate, continuous conductors, one on each side of the passage travel of the boards 30, traversing the length of the respectively associated mounting plates lGl, 188. The conductors 195, 196, are electrically connected, by means of suitable lead lines 200, to conduct electricity to the upper ends of the printed circuit boards 30, through a plurality of parallel downwardly extending spring fingers 201, 202, that arc incompletely severed from the conductors l9S, 196, by vertical slits. The fingers 201, 202, e~tend inwardly towards the passage of travel of the boards 30 being delivered there-between, with the spring fingers 201 and 202 bcing in biased engagement with the opposite sides of the boards being delivered therebetween, to springingly engage the boards 30 and make electrical connection with those upper ends of the boards ~hat are above the liquid level in the apparatus (the liquid level being below the lower surfaces of the plates 157, 170 in Figure 7, although not specifically illustrated). As in the embodiment of the invention described earlier, the conductive portions of the upper ends of the boards conventionally communicate with the tabs (not sllowll) at the lower ends of the boards in Figure 7, as printed circuit boards are designed.
It will be also apparent that in the embodiment of Figures 7 and 8, as in the earlier embodiment, the lower ends or tabs of boards 30 function as electrodes, that are immersed, below the liquid level, in a bath of electrolyte, and the electrolyte is provided with immcrsed electrodes in the form of nozzles, in banks along each side of the path the plate tabs, and a means for gencrating an electrical potential between the electrodcs, is likewise provided, as with the earlier discussed embodiment.
The apparatus may comprise a plurality of modules connec-ted together, end-to-end, in accordance with the principles and connection means of United States Patent Number 4,015,706. To this end, the modules may be provided with dowel pins 120, for alignment of modules one to the other, by insertion of the pins 120 into mating holes 121, of a next adjacent module. Also moun-ting blocks 122 may be utilized, having tapped holes 123 therein, for connection by means of threaded members, of a module having a mounting block 122 along each side, with an adjacent end of a next-adjacent module, by means of the threaded members that engage the tapped holes 123, passing through holes 124 of a next-adjacent module. In this manner, connection and alignment means is pro-vided, from module-to-module. Also, the drive rod 86 may be con-structed to be substantially coextensive with the length of the apparatus 20, between walls 22 and 21 thereof, as a single drive rod. The ends of the drive rods may be likewise connected by a plugging type connector member, in accordance with the disclosure of United States Patent Number 4,015,706.
A filter may be provided for the electrolyte in the sump 32, which filter may be removably disposed therein, in accordance with the disclosure of United States Patent Number 3,776,800.
It will be apparent from the foregoing, that the conduc-tor portions of the plates themselves 30, function as electrodes, with respect to those portions of the plates 30, that comprise the tab portions 66 that are to be electroplated. These tabs 66 will generally comprise the cathodes. The anodes will preferably be the nozzles 40, and preferably the complete nozzle banks 37, ~203505 38, and connector members 45 and 47, electrically connected to a suitable power source by means of the leads 49. It will further be understood that generally an AC power source will be utilized, converted by means of a recti-fier (not shown) to a suitable source.
It will further be understood that, while the disclosure above is principally directed toward electroplating gold in the form of insoluble gold ions in the electrolyte, onto the tabs 66 of printed circuit boards, as part of the electroplating process, it will be understood that apparatus in accord-ance with the structure of apparatus 2Q may be utili~ed to perform preliminary functions, prior to the actual gold electroplating. For example, solutions other than electrolytes may be utilized in apparatus 20, such as degreasing solutions, whereby the printed circuit boards would be delivered to a next ad~acent module, where perhaps a nickel plating would take place, in accordance with the electroplating techniques taught herein. Thereafter, the gold elec-troplating may take place, followed by suitable rinsing, blow-drying opera-tions, as may be necessary to complete the entire process.
It will also be understood that, with respect to the electrical connection with the printed circuit boards, at the upper ends, suitable mater-ials may be employed. For example, the guides that form the track 92 may be of 2q polypropylene construction, as desired, as may be the guide member 61 that forms the lower guide track.
It will be apparent also that various other modifications may be employed in the apparatus of this invention, for example, baffles may be util-ized in the bath 43, for obtaining desired flow situations, as may be desired.
Additionally, aside from those components that actually function as electrodes, the various components of this apparatus, particularly those in the bath and in the im~ediate vicinity of the bath, will either be coated with, or comprised of electrically nonconductive materialO
It will also be apparent that while this process is directed toward electroplating gold onto tabs of plates, the equipment and techniques disclosed herein may be utilized for electroplating other metals onto printed circuit board portions, or even onto other members that are to be electroplated, if such other members have the necessary structural features to accommodate use in the apparatus of this inventionO Accordingly, various modifications may be made in the details of construction, as well as in the use and operation, all within the spirit of the invention as defined in the appended claims.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for localized treatment of tabs of printed circuit boards and the like comprising: means defining a treatment zone; conveying means for conveying the tabs of printed circuit boards on lower ends thereof, through the treatment zone, with the boards in generally upright disposition along a predetermined generally vertical path; delivery means for delivering a treatment fluid to boards in the treatment zone; with said conveying means comprising a plurality of opposed roller pairs along said path outside of said treatment zone, with one roller of each said pair being mounted on each side of said path, for board engagement therebetween; and with the opposed rollers of each said pair having resilient board-engaging surfaces and are mounted for rotation relative to each other to be in interference fit with a board upon receiving a board therebetween.

2. The apparatus of Claim 1, wherein one roller in each said pair is a driving roller and the other roller in each said pair is an idler roller, with a plurality of said idler rollers being mounted for rotation in a common frame, and wherein means are provided for adjustably positioning said frame laterally toward and away from said path, from accommodating boards of different thicknesses.

3. Apparatus for localized electroplating of tabs of printed circuit boards and the like, comprising: means defining a bath zone of electrolyte;
conveying means for conveying printed circuit boards such that tabs on lower ends thereof are carried through the bath zone, with the boards in generally upright disposition along a predetermined generally vertical path; delivery means for delivering a sufficient flow of electrolyte to the bath zone, to maintain a bath depth of a predetermined desired level; means automatically and serially engaging portions of the boards that are out of the solution and making continuous electrical contact therewith as the boards are conveyed through the solution, whereby the immersed board tabs function as electrodes;
wherein said conveying means comprises a plurality of opposed roller pairs along said path outside of said bath zone, with one roller of each said pair being mounted on each side of the path, for board engagement therebetween;
wherein the rollers in each said pair are in resilient biased-together engagement for resiliently engaging boards in sandwiched relation therebetween.

4. The apparatus of Claim 3, wherein one roller in each said pair is a driving roller and the other roller in each said pair is an idler roller, with each idler roller being separately slideably mounted for movement toward and away from its associated drive roller.

5. The apparatus of Claim 4, wherein pneumatic bladder means is provided, disposed against said idler rollers for urging said idler rollers toward said drive rollers.

6. The apparatus of Claim 5, wherein said idler rollers are each mounted in respectively associated slideable idler mounts, and wherein stationary means is provided on said apparatus, and wherein said bladder means comprise a single elongate bladder located between said slideable mounts and said stationary means, along substantially the length of the apparatus.

7. The apparatus of Claim 5, including means disposed above said predetermined level, for wiping the printed circuit boards against electrolyte contact above the level of said wiping means; said delivery means including a bank of electrolyte delivery nozzles along said path; with means making electrical connection with said nozzles, whereby said nozzles function as immersed electrodes; and including means for generating an electrical potential between said electrodes.

8. The apparatus of Claim 5, wherein said means for making electrical contact with the boards includes elongate continuous conductor means carried on each side of the board path, with said conductor means having a plurality of conductive spring fingers carried serially thereby, and extending trans-versely into the path of the boards for making electrical engagement with said boards.

9. The method of localized electroplating of tabs of printed circuit boards and the like, comprising the steps of: providing a bath zone of electrolyte; conveying printed circuit boards through the bath, in generally upright disposition, along a predetermined generally vertical path, with the tabs being carried through the bath; delivering a sufficient flow of electrolyte to maintain a bath depth of a predetermined desired level;
automatically and serially engaging portions of the boards and making electrical contact therewith out of the level of the bath, as the boards are carried through the bath, thereby making the board tabs function as electrodes in the electrolyte bath; wherein said conveying step includes engaging the boards serially between opposed pairs of rollers, one of which is a drive roller and the other a slideable idler roller, and applying continuous resilient force to the idler rollers to urge them toward their associated drive rollers.