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Date: | Thu, 14 Sep 95 17:19:18 EST |
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Help! I have a question concerning the use of anode baskets in place of
anode bars. What are the advantages and disadvantages of using anode
baskets? Which shape of basket is better, round or rectangular? Does any
one out there have any technical data available?
You can reach me at Details Inc. (714)-630-4077
Paul Walker
Sr. Process Eng.
Paul:
We've been using anode baskets for acid copper plating for over 10
years here.
Converting to anode baskets vs solid bars can result in a significant
cost savings as a result of not having to send "useable" copper out to
a reclaimer. The delta between the cost of new anodes and the salvage
value of the "scrap" copper is this savings. This savings can often pay
back the capital expenditure for the baskets in a reasonable (12-18
months?) period.
In my opinion, the round baskets offer more flexibility for anode
location as well as anode area. I think it's easier to "fine tune"
anode placement and anode area with the round vs the rectangular
anodes.
There are several "caveats" to be aware of when converting to baskets
from bars.
Be careful of the design of the baskets. I've found that they are
available made from either expanded metal mesh or perforated metal. The
expanded metal mesh baskets are often much lower cost than the
perforated metal but are also more easily damaged unless they are well
reinforced with solid titanium rings and vertical ribs.
Be careful of the guage thickness of the titanium used. Lower cost
baskets will have a thinner guage titanium. The strength and
conductivity of the basket may suffer as a result. Compare different
suppliers for this.
Depending on how deep your tanks are and how long your baskets have to
be, you may find a top-to-bottom plating thickness variation due to the
lower conductivity of the titanium vs solid copper. The design and
thickness of the titanium impacts this also.
One of the big problems with baskets is "bridging". As the copper
anode chunks corrode, a "bridge" may form somewhere down in the basket
which doesn't allow the fresher chunks on top to fall down in the
basket. The anode material below the bridge corrodes away over time and
a void results below the "bridge". Your anode area then changes and
your plating distribution becomes a problem (potentially overplating an
underplating within the same plating load.) People try to avoid this by
shaking the baskets or poking them with a rod before topping them off
with fresh anode material. The round "ball" anode material is an
attempt to avoid this; however, it is common to pay a premium for the
"balls" over the "chunks". We have also found that we can still get
bridging with "balls".
Another "problem" is how to "top off" the baskets with fresh material
and when to do this. You want to "top off" the baskets often enough so
that your anode area stays reasonably constant. The other problem
depends on access to the baskets: i.e., whether you are dealing with a
small "hand" tank or a wide automatic plating line. No matter how
carefully the anodes are topped off, some material seems to find its
way to the tank bottom. Over time, this accumulates and you find you
need to empty your plating tank to remove it.
I've also found that periodically it is worthwhile to remove the
baskets, empty them, replace the anode bags and refill them with fresh
anode material. Otherwise, you never know the condition of the bags,
baskets, sludge build up, etc.
Hope this helps. Contact me if you need any more information. Good luck
with your decision.
John Monaghan
Chem. Eng. Mgr.
Hadco Corp. - Derry Division
[log in to unmask]
The net of it all is that baskets can yield a cost savings but they
still require some "maintenance" other than just "fill 'em and forget
'em".
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