Electroplating apparatus for plate-shaped workpieces

An electroplating apparatus for plate-shaped workpieces, particularly printed circuit boards which are guided through an electrolytic solution in a horizontal path for the application of metal has a conveying arrangement comprising laterally arranged upper band drives and laterally arranged lower band drives whereby the workpieces are entrained in a friction-actuated fashion between a lower run of the upper band drive and an upper run of the lower band drive. In addition, a sealing wall is arranged between the upper and lower runs of each of the band drives to produce a sealing arrangement for a laterally exposed edge of the workpiece, which is engaged by a contacting mechanism for the cathodic contacting of the workpiece projecting through the band drives.

RELATED APPLICATION 
The present invention is related to my U.S. Pat. application Ser. No. 
394,725, filed Aug. 16, 1989, and to my U.S. Pat. application Ser. No. 
394,536, filed Aug. 16, 1989. 
BACKGROUND OF THE INVENTION 
The present invention is directed to an electroplating apparatus for 
plate-shaped workpieces, particularly printed circuit boards, which 
workpieces are conducted through an electrolyte solution in a horizontal 
path for the application of a metal thereto. 
An electroplating apparatus for electroplating plateshaped workpieces 
moving in a horizontal path is disclosed in U.S. Pat. No. 4,385,967, whose 
disclosure is incorporated herein by reference thereto, and which was the 
basis of German DE-A 32 36 545. In the apparatus of this patent, 
plate-shaped workpieces are conducted through an electrolyte solution in a 
horizontal path. Feed of the workpieces occurs by driven contact wheels 
that are arranged at one side in the treatment cell and also 
simultaneously serves as a contacting mechanism for the cathodic 
contacting of the workpieces. Shieldings extending in the throughput 
direction and having sealing ledges press against the respective 
workpieces are provided for protecting the contact wheels against the 
electrolyte solution. A special guide fastener, which is arranged at the 
side of the treatment cell opposite to the contact wheels, is arranged for 
guiding and holding the workpieces. 
In the electroplating apparatus described above, the employment of the 
sealing ledges cannot adequately prevent the access of electrolyte 
solution to the lateral contacting region of the workpiece and to the 
contact wheels. As a consequence of these incomplete seals, spongy metal 
depositions occur in the contact region, a rapid deterioration of the 
rolling contact occurs and unfavorable distribution of the layer 
thicknesses of the electrodeposited layers or, respectively, a great 
scatter of the layer of thicknesses, will occur. 
U.S. Pat. No. 4,776,939, whose disclosure is incorporated herein by 
reference thereto and which was based on German Application No. 36 24 481, 
discloses an electroplating apparatus wherein the conveyor means is 
constructed as an endless circulating, driven row of individual conveyor 
elements that retain the lateral edge of the plate-shaped workpiece and 
move in a conveying direction. At the beginning of the conveying path, 
means are provided to create a grasping of the plate-shaped workpiece by 
the conveyor elements, and at the end of the conveyor path, means are 
provided to create a release of the plate-shaped workpiece by the conveyor 
elements which are being passed through the electrolysis chamber. Apart 
from the beginning of the grasping and the beginning of the releasing, no 
relative movement between the conveyor element and the workpiece edges 
will occur so that the wear phenomena or, respectively, abrasion phenomena 
of the conveyor elements is avoided. The conveyor elements can, thus, also 
simultaneously serve for supplying power to the plate-shaped workpiece. 
U.S. Pat. No. 4,755,271, whose disclosure is incorporated herein by 
reference thereto and which is based on the same German Application as 
European Application A-0 254 962, discloses another type of electroplating 
apparatus of the above-mentioned type, wherein the contacting mechanism is 
formed by forceps-shaped contact clamps laterally displaceable together 
with the workpiece. These clamps are placed on an endless drive which, 
preferably, serves as a displaceable carrier of the contact clamps. The 
contact clamps also simultaneously serve as conveyor elements for the 
throughput of the workpiece. The contact clamps are shielded from the 
access of the electrolyte solution by a seal laterally extending in the 
throughput direction and resiliently pressing against the respective 
workpiece. 
SUMMARY OF THE INVENTION 
In electroplating apparatuses of both types of species, the object of the 
present invention is to further improve the shielding of the contact 
mechanism from contact with the electrolyte solution and to, thus, 
guarantee a better cathodic contacting of the workpiece. 
In order to achieve these objects, an electroplating apparatus for 
plate-shaped workpieces, particularly printed circuit boards which are 
conducted through a container of electrolytic solution in a horizontal 
path for the application of metal, comprises at least one conveyor means 
arranged laterally relative to the throughput path and being composed of 
an upper band drive and a lower band drive for the friction-actuated 
entrainment of the workpiece between a lower run of the upper band drive 
and the upper run of the lower band drive for movement through the 
solution, a sealing wall being arranged between the upper run and lower 
run of each of the band drives and at least one contacting means being 
arranged laterally relative to the path of the workpiece for cathodically 
contacting the lateral edges of the workpiece projecting laterally beyond 
the band drives. 
The lateral shielding of the contact mechanism is, thus, undertaken by the 
sealing bands firmly pressed against the surfaces of the workpiece whereby 
these sealing bands, as conveyor elements, simultaneously create the 
friction-actuated entrainment of the workpiece. Thus, with an especially 
low structural outlay and cost, a very good lateral shielding of the 
contacting means or mechanism against the access or contact of electrolyte 
solution is, thus, achieved. Moreover, no relative movement between the 
conveyor elements and the workpiece bands is established here, and, thus, 
wear phenomena of the conveying elements is avoided or eliminated. 
In accordance with a preferred development of the invention, at least, 
respectively, one conveyor means is arranged on each side of the through 
path so that an especially reliable guidance of the workpiece is achieved. 
Since a two-sided shielding or, respectively, sealing occurs in this case, 
at least, respectively, one contacting mechanism can be arranged at each 
side of the throughput path for further improvement of the cathodic 
contacting. 
As a result of the effective shielding of the contacting region, a 
stationarily arranged contacting mechanism can, thus, also be employed for 
wiper contacting of the workpiece. An especially high-grade, cathodic 
contacting is achieved in this case when the contacting mechanism 
comprises a plurality of contact spring pairs arranged at a distance from 
one another, whose contact springs lie opposite one another and press 
resiliently against the upper side and against the under side of the 
workpiece. 
According to another modification, however, the contacting mechanism 
comprising contacting means synchronously corunning with the workpiece can 
also be provided. Thus, the relative movement in the workpiece and the 
contacting means present in the wiper contacting is eliminated in this 
particular instance. The contacting means are then, preferably, arranged 
on an endless drive belt that can be easily synchronized with the conveyor 
means. 
Accordingly to a first embodiment of this modification, the contact means 
can be formed by an endless circulating bandshaped brush arrangement. It 
is provided, according to a second preferred embodiment, that the 
contacting means is formed by a plurality of contact spring pairs secured 
to an endless circulating metal band at a distance from one another, and 
the contact springs thereof lie opposite one another to resiliently press 
against the upper surface and the lower surface of the workpiece. In both 
embodiments, a cleaning means for cleaning the circulating contacting 
means can then be arranged in the region of a returning run or side of the 
endless band or belt. The cleaning means, which is preferably formed by an 
electrolytic demetalization cell, then effects an enhancement of the 
contactibility and, in particular, also effects the removal of the metal 
depositions that potentially occur on the contacting means. 
Further advantages and features of the invention will be readily apparent 
from the following description of the preferred embodiments, the drawings 
and claims.

DESCRIPTION oF THE PREFERRED EMBODIMENTS 
The principles of the present invention are particularly useful when 
incorporated in a conveying means, generally indicated at Te, for 
conveying printed circuit boards Lp through an electrolyte solution (not 
illustrated) in a horizontal path or attitude in the direction of arrow 
Pf1. The conveying means Te is composed of an upper band drive Bto and a 
lower band drive Btu, wherein each of the band drives includes a band B 
which is endlessly circulating over two end rollers Ur, which are arranged 
at a distance to one another, and, thus, each of the bands B has an upper 
run and a lower run. 
The end sheaves or rollers Ur for the upper band drive and for the lower 
band drive rotate in the direction of arrows Pf2 so that a printed circuit 
board Lp is drawn in on the left-hand side of FIG. 1 and is moved in the 
direction of the arrow Pf1 to be discharged on the right-hand end. As 
illustrated, the board will be gripped between the lower run of the upper 
band drive and the upper run of the lower band drive. 
In the lateral regions of the printed circuit board Lp, the bands B will 
lie tightly against the upper surface and against the lower surface over 
the entire length so that no electrolyte solution can pass between the 
band B and the printed circuit board Lp. This sealing effect can be 
further intensified by utilizing bands B of a basically, especially 
elastic substance, such as rubber or the like. A comparative sealing 
effect then also occurs between the bands B and a sealing wall Dw that are 
arranged between the upper runs and the lower runs of each of the band 
drives Bto and Btu and are pressed tightly against the end sheaves Ur. 
When the lower run of the lower band drive Btu also lies tightly against a 
floor Bo of a container containing the electrolyte solution, then the 
upper band drive Bto and the lower band drive Btu, in combination with the 
sealing walls Dw, form a shielding that at least largely prevents the 
lateral emergence of any electrolyte solution. The end walls in the 
container of the electrolyte solution can also be used instead of having 
the sheaths Ur press against the ends of the sealing walls Dw. These end 
walls are provided with appropriate slots for the passage of the printed 
circuit board and of the band B. However, the rollers Ur continue to be 
present in this case as component parts of the conveyor means Te. 
As illustrated in FIGS. 2 and 3, the drive arrangement Te of FIG. 1 is 
disposed in a bath container Bb of an electrolyte plating apparatus. The 
bath level of the electrolyte solution contained in the bath container Bb 
is thereby referenced Bsp. It may also be seen that a horizontally 
aligned, upper anode Ao that is composed of a basket Kb of expanded metal 
and of spherical anode materials Am is situated at a slight distance above 
the throughput path of the printed circuit board Lp. A lower anode Au that 
is likewise horizontally aligned is arranged at a slight distance under 
the throughput path of the printed circuit board Lp and this lower anode 
Au is constructed as an expanded metal sieve and, for example, is composed 
of a platinum-plated titanium. In contrast to the upper anode Ao that, for 
example, contains the copper balls as an anode material Am, the lower 
anode Au is, thus, an insoluble anode. 
The cathodic contacting of the printed circuit boards Lp occurs by 
contacting mechanisms or means Kv1, which are arranged on both sides of 
the throughput path, and grasp the lateral edges of the printed circuit 
board Lp which project beyond the conveyor means Te that are, likewise, 
arranged on both sides. Each of the two contacting mechanisms Kv1 is 
thereby composed of an upper live rail Sso (see FIGS. 3 and 4) that 
carries a plurality of upper contact springs Kfol arranged at a distance 
from one another and of a lower live rail Ssu that carries a plurality of 
lower contact springs Kful arranged at a distance from one another. The 
upper contact springs Kfol and the lower contact springs Kful lie opposite 
one another in pairs and thereby provide a reliable wiping contacting of 
the printed circuit board Lp. 
As may be seen without further ado, particularly in the cross section shown 
in FIG. 3, the two conveyor means Te in combination with the sealing walls 
Dw also fulfill the function of sealing devices that protect the 
contacting mechanisms Kv1 against deterioration due to access or contact 
with the electrolyte solution. 
In the electroplating apparatus illustrated in FIG. 4, it can be seen that 
the two end walls of the bath container Bb are provided with horizontal 
slots Sz at the level of the throughput path identified by the arrow Pfl. 
These slots Sz enable the passage of the printed circuit boards Lp into 
the container and out of the container. The interior between an upper 
terminating hood (not shown in FIG. 4) and the bath container Bb is 
provided with an extractor Ag at one side that is connected to a central 
extractor or suction means for producing a vacuum or under-pressure in 
this space. A drive shaft Aw proceeding in the longitudinal direction 
extends under the extractor Ag, and this drive Aw drives the two 
illustrated upper end rollers Ur by bevel gear wheels that cannot be seen 
in greater detail. 
The lateral delivery of the electrolyte solution into the bath container Bb 
(not shown in FIG. 4) and the discharge via a discharge connector As 
introduced into the floor Bo are dimensioned such that an upwardly 
directed flow indicated by the arrows Pf3 occurs via the 
through-contacting holes Dk of the printed circuit boards Lp. Insofar as 
other conditions are satisfied, this pronounced flow guarantees a 
qualitatively high-grade voltaic coating and strengthening of the 
through-contacting holes. 
Departing from the cross sections shown in FIGS. 2 and 3, FIG. 4 shows an 
alternate wherein a horizontally aligned upper plate Po that extends 
transversely relative to the throughput direction is arranged between the 
two upper sealing walls Dw and the two upper runs of the upper band drive 
Bto. In order to be able to replace the anode material Am, the upper plate 
Po is provided with an opening that can be closed with a cover De. In a 
similar fashion, a lower plate Pu, that otherwise extends transversely 
relative to the throughput direction is arranged between the lower runs of 
the two lower band drives Btu (also shown in FIG. 1) and the lower edge 
surfaces of the lower sealing walls Dw. 
FIG. 5 shows a modification of the electroplating apparatus shown in FIG. 
4, wherein the contacting means or mechanism Kv2 having an endless 
circulating, band-shaped brush arrangement Ba, is provided instead of the 
contacting mechanism Kv1. This brush arrangement Ba circulates over two 
rollers Ro whereby one roller Ro is driven in a direction of arrow Pf4 so 
that the brush arrangement Ba co-runs synchronously with the printed 
circuit boards Lp. The supply of cathode current occurs by a stationarily 
arranged live rail Ssl onto which the brush arrangement Ba slides. Thus, 
the current flows from the live rail through the brush arrangement Ba into 
the respective printed circuit boards Lp. 
If undesirable metal depositions and agglomerations form on the brush 
arrangement Ba due to a potential emerging of the electrolyte solution, 
then these are in turn removed by a cleaning mechanism RE in the region of 
a return run of the brush arrangement Ba. This cleaning means RE is 
constructed as an electrolytic demetallization cell that contains an 
electrolyte solution, preferably the electrolyte solution employed in the 
electroplating apparatus. The demetalization then occurs with an anodic 
contacting of the brush arrangement Ba relative to a cathode situated in 
the cleaning mechanism RE. 
Another modification of the contacting means or mechanism is illustrated by 
the contacting means or mechanism Kv3 in FIG. 6. The contacting mechanism 
Kv3 is also a contacting means that coruns synchronously with the printed 
circuit boards Lp and is formed by a plurality of contact spring pairs 
secured to an endless circulating metal band Mb at a distance from one 
another. Each of the contact pairs is composed of an upper contact spring 
Kfo2 and a lower contact spring Kfu2, which lie opposite one another. The 
lateral edge of the printed circuit board is accepted between these upper 
and lower contact springs, which apply a certain resilient contact 
pressure thereto. A power supply to the metal band Mb occurs by a live 
rail Ss2 which is arranged stationarily along the back side of the band Mb 
and forms a contact therewith by brushes Br2. The live rail Ss2 is 
preferably formed by a titanium-cladded, solid copper conductor. The 
brushes Brs are preferably composed of copper, whereas titanium has proven 
extremely good as a metal for the metal band Mb and for the contact 
springs Kfo2 and Kfu2. The cleaning or respective demetallization of the 
contact springs Kfo2 and Kfu2, according to the principles shown in FIG. 
5, are possible by providing a cleaning means RE to engage a return run of 
the band and springs. 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent granted hereon all such modifications as reasonably and 
properly come within the scope of my contribution to the art.