U.S. patent number 3,905,827 [Application Number 05/518,564] was granted by the patent office on 1975-09-16 for etchant rinse method.
This patent grant is currently assigned to Chemcut Corporation. Invention is credited to John Alfred Dunkelberger, Jr., Daniel L. Goffredo.
United States Patent |
3,905,827 |
Goffredo , et al. |
September 16, 1975 |
Etchant rinse method
Abstract
Residual etchant, such as acid and the like remaining on
articles such as printed circuit boards that have been etched,
contains a metallic chemical component, such as copper. When this
residual etchant is rinsed from the articles (such as printed
circuit boards), it contaminates the water of the rinse. The
chemical replacement of copper ions in the rinse with aluminum ions
by passing the rinse through a basket filled with aluminum
turnings, and recycling the rinse thus passed back for reuse at the
rinsing station continuously renders the rinsing water free of
copper, to permit periodic discharge of the rinse water to sewage
or the like.
Inventors: |
Goffredo; Daniel L. (Riverton,
NJ), Dunkelberger, Jr.; John Alfred (Centre Hall, PA) |
Assignee: |
Chemcut Corporation (State
College, PA)
|
Family
ID: |
26885811 |
Appl.
No.: |
05/518,564 |
Filed: |
October 29, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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190136 |
Oct 18, 1971 |
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Current U.S.
Class: |
75/726; 134/10;
210/688; 210/712; 210/719; 210/912; 216/93; 216/105 |
Current CPC
Class: |
C23F
1/08 (20130101); B08B 3/022 (20130101); C02F
1/705 (20130101); H05K 3/26 (20130101); Y10S
210/912 (20130101); C02F 2103/346 (20130101); H05K
2203/075 (20130101); H05K 2203/0766 (20130101); C02F
2101/20 (20130101); H05K 2203/1509 (20130101) |
Current International
Class: |
C23F
1/08 (20060101); B08B 3/02 (20060101); C02F
9/00 (20060101); H05K 3/26 (20060101); B08B
003/02 (); B08B 003/10 (); B08B 007/04 () |
Field of
Search: |
;134/10,13,109,111,131,151,199,83 ;156/19,345 ;210/38,287,433
;75/109,11BE ;204/32R,35R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Caroff; Marc L.
Attorney, Agent or Firm: Paul & Paul
Parent Case Text
This is a division of application Ser. No. 190,136 filed Oct. 18,
1971.
Claims
What is claimed is:
1. A method of removing residual chemical etchant from articles
such as printed circuit boards and the like that have been
subjected to etching of copper portions thereof, comprising the
steps of conveying etched articles along a predetermined path,
spraying the articles with a water rinse during their conveyance
along the path and thereby accumulating a significant concentration
of copper ions in the rinse water, collecting the rinse water in a
reservoir, providing a tank of particulate material, which material
is capable of replacing copper ions in the rinse with its own ions,
continuously delivering rinse water from the reservoir
simultaneously to the tank for transfer through the particulate
material wherein the ion replacement is effected and for spraying
the articles, and continuously recycling rinse water that has been
subjected to the ion exchange to the reservoir, for reuse in
spraying.
2. The method of claim 1, wherein the particulate material
comprises aluminum particles for replacement of copper ions in the
rinse water with aluminum ions.
3. The method of claim 2, wherein rinse water delivered to the tank
is pumped thereto from the reservoir concurrently with pumping of
rinse water for spraying, through a common bifurcated delivery
line, and wherein rinse water is delivered directly to the
reservoir following the ion exchange.
4. The method of claim 1, wherein the rinse water is periodically
discharged to a sewage line and replaced as the ion concentration
of the replacing ions from the particulate material in the rinse
water reaches a predetermined level.
Description
BACKGROUND OF THE INVENTION
In the art of etching printed circuit boards and the like, it has
been commonplace to rinse acid etchants from the printed circuit
boards, for purposes of "cleaning" the acid from the boards, in
order that the boards may be subsequently handled by personnel, and
also to assure the termination of the etching process, on copper
components of the board. Such washing or rinsing has conventionally
been done by spraying the boards with a water rinse, and either
continuously or periodically replacing the water rinse, with used
water rinse being discharged to sewage or the like. However, such
used water rinse in accordance with the above-mentioned prior art
techniques has contained copper ions therein, and such has been
found to cause undesirable ecological effects upon streams,
waterways and the like, into which the used rinse eventually finds
its way from sewage.
Furthermore, the copper contained within the acid rinsed off the
boards in accordance with these prior art techniques has been
permanently lost.
SUMMARY OF THE INVENTION
The present invention is directed toward providing an apparatus and
method whereby recycling of the rinse water is possible without
building up an undesirable level of copper concentration in the
rinse water, and whereby the rinse water is not contaminated by
copper, so that the same may be discharged into conventional sewage
lines, streams, etc., without producing damaging environmental
effects. A portion of the rinse water being delivered to spray
nozzles passes from the reservoir of rinse water to and through a
particulate material (preferably aluminum turnings), and the rinse
water is dispersed therethrough, eventually being returned to the
rinse reservoir. During its passage through the aluminum turnings,
a chemical replacement of copper ions in the rinse is effected, by
replacement with aluminum ions, with the copper ions being reduced
to metallic copper, and with the aluminum being oxidized and
flowing into solution in the rinse water. The rinse water thus
accumulates an aluminum ion concentration, which may periodically
be discharged as desired, without producing undesirable
environmental effects.
Accordingly, it is a primary object of this invention to provide a
novel method of treating etchant rinse water.
It is a further object of this invention to provide a novel method
of replacing copper ions in etchant rinse water with aluminum
ions.
It is another object of this invention to provide a novel apparatus
for rinsing etchant reactants from articles that have been etched,
wherein such apparatus involves chemical replacement of unwanted
metallic ions in the rinse medium.
Other objects and advantages of the present invention will be
readily apparent to those skilled in the art from a reading of the
following brief descriptions of the drawing figures, detailed
description of the preferred embodiment, and the appended
claims.
IN THE DRAWINGS
FIG. 1 is a transverse sectional view through the several
components of a rinsing apparatus of this invention.
FIG. 2 is a longitudinal sectional view through a portion of the
rinsing apparatus illustrated in FIG. 1, and illustrating the
manner in which the rinse is sprayed onto printed circuit boards or
the like passing through a rinse chamber from an etching chamber or
the like.
Referring to the drawings in detail, reference is first made to
FIG. 2, wherein an upstream chamber 10 is illustrated, as
comprising an etching chamber, or if desired, a chamber for first
physically removing etchant from printed circuit boards 11 or the
like conveyed therethrough, by means other than water spraying. The
printed circuit board 11 for which this apparatus has been
developed, is then delivered into a rinsing chamber 12, passing
along a plurality of driven rollers 13, which rotate in a clockwise
direction as viewed in the illustration of FIG. 2, for movement of
the printed circuit board 11 in the direction of the arrow 14 of
FIG. 2, through the chamber 12 for eventual discharge through the
outlet 13 thereof, to a drying station or the like.
The board 11, upon its delivery to the chamber 12 may have residual
components of an etching acid, such as ferric chloride thereon,
that has been used to etch unmasked copper portions of the printed
circuit boards, and such residual etchant thus contains a certain
copper content.
The board 11 then passes between upper and lower sets of spray
nozzles 15 and 16, that are supplied with water under pressure, for
spraying the board 11 through a certain zone such as that indicated
in FIG. 2, with the zones of spray of the nozzles combining
transversely of the machine, in order to completely spray a board
11 carried therebetween, as will be more clearly apparent with
reference to the illustration of FIG. 1. The upper spray nozzles 15
are connected to rinse water header 17, and the lower spray nozzles
16 are each connected to a lower rinse water header 18, with the
headers 17 and 18 being supplied with rinse water from a common
delivery line 20. After spraying of the board 11 with rinse water
passing through the nozzles 15 and 16, the rinse water 21 drops
into a reservoir 22, and such rinse water 21 and the reservoir 22
now has a slight concentration of copper ions therein. Rinse water
21 is delivered from a chamber 22, by a pump 23, or other suitable
device, which receives the rinse water 21 at a lower inlet 24
thereof, and delivers the same through an outlet line 25, with the
pump 23 being driven by an electrical motor 26 or the like disposed
outwardly of the chamber 22, but connected to the pump 23 through a
rotatable shaft 27 that passes into the chamber 22 from outside
thereof, to drive the submerged pump 23.
Rinse water is thus delivered through the line 25, outwardly of the
chamber 22, with the delivery line 25 being bifurcated at the
piping tee 29, with some of the rinse water being delivered to the
spray nozzles 15 and 16, through the line 20, and some of the rinse
water being delivered through a replacement chamber 28, and back
into the reservoir 22 through a return line 30, selectively
openable upon actuation of a switch 31 or the like, as desired,
whereby rinse water is delivered to the replacement chamber 28, as
a parallel loop to that delivered to the spray nozzles 15 and 16.
Thus, rinse water enters the replacement chamber 28, being
delivered thereto by a suitable piping line 32, and passing through
a generally open shut-off switch 33, entering the replacement
chamber 28, through the bottom 34 thereof, at a central opening
thereof, for passage outwardly of a plurality of holes 35, or other
suitable perforations in the outer surface of a hollow cylindrical
upstanding standpipe 36, as illustrated in FIG. 1.
A removable tank 37 is provided, inwardly of the replacement
chamber 28, the bottom of which has a blind hole therein for
facilitating the disposition of the tank 37 over the standpipe 36,
and with the sides of the blind hole 38 in the tank 37 facilitating
the passage inwardly of rinse water into the interior 40 of the
tank, as such rinse water passes through perforations 35 of the
standpipe 36. The tank 37 is constructed as a basket, with the
outer cylindrical surface 41 thereof also being perforate, and with
the basket being filled with a particulate material such as
aluminum turnings whereby the rinse water 21 delivered through the
line 32 will pass through the aluminum turnings, to be discharged
through the tank 37, but passing through perforations in the outer
wall 41 thereof. It will be noted that the outer surface of the
tank 41 is spaced inwardly of the inner surface of the chamber 28,
to form an annular void therein, for passage of water upwardly,
inasmuch as the water is under pressure from the pump 23, and with
the water thus being redelivered through the line 30 as aforesaid,
into the chamber 22.
The tank 37 is also provided with a handle 43 whereby the same may
readily be grasped and removed from its position over the standpipe
36, upon opening the lid 44 of the chamber 28, whenever the
concentration of copper within the aluminum turnings necessitates
replacement of the tank 37, or of the turnings carried therein.
It will be apparent from all of the foregoing, that during the
passage of the rinse water through the aluminum turnings within the
tank 37, the dissolved copper content within the rinse is
chemically replaced with aluminum from the aluminum turnings, and
the copper ions removed from the rinse are reduced to metallic
copper and aluminum is oxidized, going into solution in the rinse
water. The water reservoir thus remains extremely low in copper ion
concentration, but will progressively increase in aluminum ion
concentration. Upon the reservoir 22 achieving an objectionable
level of aluminum ion concentration, the rinse water 21 therein may
be discharged to sewage or the like, without causing contamination
of sewage lines, waterways, or the like.
The herein discussed invention is significant in that it provides a
simple and low cost means of eliminating objectionable copper ions
from etchant rinse water. Accordingly, a highly desirable
anti-pollution feature is encompassed by the present invention,
which replaces copper ion concentration in rinse water with more
acceptable aluminum ions.
While displacement reactions themselves are previously known, for
removing copper from solution generally, and wherein such processes
are generally known as "cementation", in the mining industry, for
example, the use of replacement ions to resolve a heretofore
difficult pollution problem for the etching industry, and
particularly for the industry relating to the etching of printed
circuit boards is highly desirable.
It will also be apparent that other types of chemical replacement
may be effected, in lieu of using aluminum particles within the
tank 37. For example, iron filings, magnesium, or any other metal
above copper in the electromotive series, or any other substance
that will effect the desired ion exchange, preferably with regard
to its adaptability to achieving the other desired ends of this
invention as set forth herein, may be utilized within the tank 37,
if desired, for replacement of copper ions with iron ions in the
solution.
Another feature of this invention is that the process permits
continuous replacement of copper ions in the rinse water, by
permitting continuous removal, by displacement reactions onto the
aluminum surfaces of the particles within the tank 37. It will,
however, be apparent that the parallel loop arrangement illustrated
in FIG. 1 is not to be construed as limiting, in that rinse water
21 from the tank 22 may pass serially first to the tank 37, and
then to the spray nozzles 15 and 16, if desired, or the
converse.
It will be apparent from the foregoing that various modifications
may be made in the details of construction of the apparatus of this
invention, as well as in the method of use thereof, all within the
spirit and scope of the appended claims.
* * * * *