Electroplating plant with opposed electrolitic cells and continuous feed of the surfaces to be treated

Abstract: An electroplating plant (1) for the electrolytic deposition of metals on flat components such as printed circuit boards (3) and the like, orientated parallel to the direction of feed and continuously supplied via a system (4) for the transmission and supply of cathode current to said boards (3), characterized in that it has at least one pair of electrolytic cells (8) each one being provided with a feed aperture (9c) and an aperture (9a) for the outflow of the electrolytic solution supplied continuously via appropriate means (7) for drawing the same from a recovery tank (6), each cell being provided with anodes (10) and means (12) for regulating the flow of the electrolytic solution, each cell of at least one of such pairs having the relevant outflow aperture (9a) located opposite that of the other cell in order to provide an empty space through which there is made to pass board (3), which is thus placed in contact with the electrolytic solution, components (11) also being provided for intercepting the fall of the solution, capable of bringing about the flow of the said solution via holes (3a) passing through board (3) for the metallization thereof.

Description: The object of this invention is a plant for the electrolytic deposition of metals on flat components such as printed circuit boards and the like with continuous feed of the boards and orientation thereof in a direction parallel to the direction of feed along the plant. There is known in printed-circuit production technology the need to place in electrical connection with one another the conducting paths made on the opposite sides of a flat panel comprised of an insulating substrate covered on both surfaces with a thin coat of conductive material such as copper. Such connection is achieved by making through-holes in the board, which are then internally covered with a layer of conductive material (copper) by electrolytic deposition carried out in suitable electroplating plants, in which there is also performed a further operation which involves covering all the copper conducting surfaces comprising the electric circuit with a further layer of protective material and solder (tin-lead alloy) as necessary for the subsequent processing of the printed circuit. The electroplating plants of known type have, however, certain disadvantages which substantially limit their production capacity; they provide for electrolytic solution interception tanks of static type which do not allow the application of high currents to the anode and cathode in order to increase the rate of deposition; additionally, feeding of the board is discontinuous and the board itself has to be raised, shifted and lowered in the various treatment tanks by means of suitable handling devices, such movements effectively resulting in corresponding down times which bring about a lengthening of the overall cycle time and ultimately a loss of output. There is therefore posed the technical problem of providing an automatic plant for the electrolytic deposition of metals on printed circuit boards which will make it possible to achieve continuous feed of the piece through the various treatment tanks and bring about constant movement of the electrolytic solution so as to be able to increase the current supplied to the anode and cathode, with a resulting increase in the rate of deposition of the material. Such technical problem is resolved according to this invention by an electroplating plant for the electrolytic deposition of metals on flat components such as printed circuit boards and the like, orientated parallel to the direction of feed and continuously supplied via a system for the transmission and supply of cathode current to the said boards, having at least one pair of electrolytic cells each provided with a feed aperture and an aperture for the outflow of the electrolytic solution supplied continuously via appropriate means for drawing the same from a recovery tank, each cell being provided with anodes and means for regulating the flow of the electrolytic solution, each cell of at least one of such pairs having the relevant outflow aperture located opposite that of the other cell in order to provide an empty space through which there is made to pass the board, which is thus placed in contact with the electrolytic solution, there being also provided components for intercepting the fall of the solution, capable of bringing about the flow of the said solution via holes passing through the board for the metallization thereof. According to the invention, the electroplating plant provides that such aperture for the supply of the electrolytic solution is connected to a vertical header, the open lower end of which is connected to the solution storage and recovery tank, and additionally that such means of drawing of the solution from the storage tank are comprised of a recirculating pump. It is furthermore provided that each cell comprises anodes consisting of substantially flat components with through-holes allowing recirculation of the electrolytic solution and inserted through the cell in a vertical direction via corresponding slots, as well as means for regulating the rate of flow in each cell, consisting of at least one tubular member located in an inclined position and substantially extending from the lower surface to the upper corner of the cell opposite the outflow aperture. In greater detail, provision is also made for such components intercepting the fall of the solution to be substantially comprised of a crosspiece located horizontally across the solution outflow aperture and provided with an outer edge relative to the cell made with an alternation of projections and recesses so that, once placed opposite the appropriate cells, each projection of one piece is located facing a corresponding recess of the opposed intercepting piece. A further feature of the plant according to the invention is that such electrolytic cells may be superimposed on one another so that the area of the electrolytic solution outflow aperture is substantially equal in height to the dimension provided for the printed circuit board to be metallized. Further details and features will become more clearly apparent from the description of an example of implementation of the plant according to the invention, given with reference to the attached set of drawings which show: In fig. 1 : an electroplating plant according to the invention shown in side view; In fig. 2 : a perspective view of an electrolytic treatment tank for the plant in fig. 1; In fig. 3 : a cross-section according to plotting plane III-III of fig. 2; In fig. 4 : a detailed schematic representation of an electrolytic deposition cell, and In fig. 5 : a detailed schematic perspective view of the components for the vertical interception of the electrolyte. As illustrated in fig. 1, electroplating plant 1 according to the invention is substantially comprised of an assembly of tanks 2 containing the treatment solutions and arranged transversally with respect to direction "A" of feed of boards 3 which are in turn located parallel to such direction of feed, which is carried out by means of a closed-loop driving device 4 shown in outline and forming the subject of a simultaneous patent application under the name of the same applicant. At least one of such treatment tanks located along plant 1 consists of a tank 5 of the type designed for the electrolytic deposition of metal and substantially formed by a bottom container 6 for the storage and recovery of the electrolytic solution; such container is closed at the top by a plate 6a to which are made integral a recirculating pump 7, suction part 7a of which is immersed in the electrolytic solution, and a double series of electrolytic cells 8 arranged one on top of the other in a vertical sense, each series being thus opposed to the other as will become clearer hereinafter. Each electrolytic cell 8 is substantially in the form of a parallelepiped 9, lower in height with respect to the base dimensions, having an open sidewall 9a and an opposed parallel wall 9b provided with apertures 9c. Parallelepiped 9 is also provided with slots 9f respectively located on the surfaces of upper base 9d and lower base 9e; through such opposed and aligned slots is inserted a flat anode 10 provided with through-holes 10a. Each open wall 9a is then partly obstructed by a component 11 for intercepting the fall of the solution, located horizontally and extending into the cell; the outward-facing edge of such intercepting piece has recesses 11a alternating with projections 11b so that when the two series of cells 8 are face to face each tooth 11b of an intercepting piece 11 is located opposite a corresponding recess 11a in facing intercepting piece 11. Each cell 8 is then completed by at least one - two in the example illustrated - tubular member 12 located in an inclined position and extending from lower surface 9e of parallelepiped 9 to the upper rear vertex thereof so as to constitute an overflow outlet capable of maintaining a constant recirculating flow of solution within cell 8 upon variation of outflow orifice 9a of such cell. Once the vertical series of cells 8 is fitted, each supply aperture 9c is place in connection with a vertical header 13, lower aperture 13a of which is immersed in electrolytic solution container 6. Such connection between aperture 9c and header 13 may also be achieved with the interposition of a flow regulating valve marked 14 in the figure and effected in the example via two coaxial tubes 14a and 14b provided with radial holes 14c, the greater or lesser alignment of which determines the greater or lesser flow of solution. The operation of the plant is as follows: After placing the two series of cells 8 in opposed position (fig. 3) on intercepting tank 6, raising to operating level the electrolytic solution within the same and making the electrical connections to anode 10, there is put into operation pump 7 which forces the solution to rise along headers 13, whence it passes through valves 14 into each cell 8 which is filled with electrolytic solution which, after passing through holes 10a of anodes 10, flows out from open walls 9a and falls by gravity in successive cascades toward the bottom, then re-enters tank 6. Simultaneously, handling device 4 grips boards 3, retaining them mechanically and supplying them with cathode current, thus causing them to advance by passing through cells 8; when board 3 (fig. 2) passes between the two series of opposed cells it determines a greater or lesser occlusion of open walls 9a as a result of its own thickness and of the number and diameter of the holes made in the said board, which greater or lesser occlusion would bring about an alteration of the rate of recirculation if it were not compensated by tubular members 12 of the overflow, which discharge from the cell more or less solution in proportion to the conditions brought about by the particular type of board inserted. In this way the cascades of electrolytic solution touch the two surfaces of the board and bring about deposition of the material; furthermore, in flowing over intercepting pieces 11 the solution tends to pass also through holes 3a of printed circuit 3, since the staggered arrangement of projections 11b and recesses 11a determines a prevalence in one sense or in the other which forces the solution to pass through board 3. It should be noted that without such arrangement there would occur a balance of pressures on the two sides of the board which would tend to obstruct the passage of the solution through the holes and prevent metallization thereof. Many variants may be used in the practical implementation of the constructional components of the various parts without thereby departing from the scope of protection of the invention as described in the following claims.

Claims: An electroplating plant (1) for the electrolytic deposition of metals on flat components such as printed circuit boards (3) and the like, orientated parallel to the direction of feed and continuously supplied via a system (4) for the transmission and supply of cathode current to said boards (3), characterized in that it has at least one pair of electrolytic cells (8) each one being provided with a feed aperture (9c) and an aperture (9a) for the outflow of the electrolytic solution supplied continuously via appropriate means (7) for drawing the same from a recovery tank (6), each cell being provided with anodes (10) and means (12) for regulating the flow of the electrolytic solution, each cell of at least one of such pairs having the relevant outflow aperture (9a) located opposite that of the other cell in order to provide an empty space through which there is made to pass board (3), which is thus placed in contact with the electrolytic solution, there being also provided components (11) for intercepting the fall of the solution, capable of bringing about the flow of the said solution via holes (3a) passing through board (3) for the metallization thereof. An electroplating plant according to claim 1, characterized in that each cell (8) is substantially in the form of a parallelepiped with an open lateral surface to determine aperture (9c) for the outflow of the electrolytic solution. An electroplating plant according to claim 1, characterized in that such aperture (9a) for the supply of the electrolytic solution is connected to a vertical header (13) the open lower end of which is connected to tank (6) for the storage and recovery of the said solution. An electroplating plant according to claim 1, characterized in that such means for drawing the solution from storage tank (6) are comprised of a recirculating pump (7). An electroplating plant according to claim 1, characterized in that such anodes (10) are comprised of substantially flat components inserted into cell (8) in a vertical sense through corresponding slots (9f) and provided with holes (10a) to allow the passage of the electrolytic solution. An electroplating plant according to claim 1, characterized in that such means for regulating the rate of flow of each cell (8) are comprised of at least one tubular component (12) located in an inclined position and substantially extending from the lower surface to the upper corner of the cell opposite outflow aperture (9a). An electroplating plant according to claim 1, characterized in that such intercepting components are substantially comprised of a crosspiece (11) located horizontally across aperture (9a) for the outflow of the solution and provided with an outer edge with respect to the cell made with an alternation of projections (11b) and recesses (11a). An electroplating plant according to claims 1 and 7, characterized in that such intercepting components (11) are made in such a way that once they are positioned facing respective cells (8) each projection (11b) of one piece is located in alignment with an appropriate recess (11a) of the opposed intercepting piece. An electroplating plant according to claim 1, characterized in that such electrolytic cells (8) may be superimposed on one another to determine an area of the electrolytic solution outflow aperture with a height substantially matching the dimension envisaged for the printed circuit board (3) to be metallized.

Inventors: SALA SERGIO, SALA, SERGIO
Applicants: SALA SERGIO, SALA, SERGIO
Application year: 1993
Main classification: C25D5
IPC codes: H05K3, C25D5