Postings listed after your response (I attached these postings) indicates
that this problem started at the same time in all three plating tanks. One
common factor of each tank would be potential drag-in contamination of dirt
or debris, possibly from the preclean process. Typical processes include
mechanical abrasion system such as pumice and/or aluminum oxide in order to
prepare the dry film surface prior to application of the dry film plating
resist.
The reason for my question was that about 4 years ago we tracked a very
similar problem (ie copper nodules, very small, hair like in appearance and
very nasty little buggers) that we eventually tracked down to a different
batch of Aluminum Oxide used in our preclean process. Detailed cross
sectioning, a whole lot of patience, a little luck and SEM analysis verified
the presence of aluminium (Al) IN THE NODULE. Follow up diagnosis verified
that the supplier of Aluminum Oxide powder had changed their supplier, who,
produced a different grade of powder that exhibited tangibly different
chemical and physical properties. This particular Aluminum Oxide powder was
causing some sort of chemical? or physical? bond to the copper surface that,
when electroplated in the subsequent electrolytic copper process, formed
these nodules. Once we changed the Aluminum oxide back to the prior
supplier's formulation, the problem ceased. Needless to say we now stipulate
the supply base for our preclean process.
SO! My question was based on the premise that the preclean process is a
common factor of the boards exhibiting the problem that may not have been
considered. It may not be Aluminum oxide but perhaps another common,
assignable cause common to the panels that exhibited the problem, orginating
in the preclean process.
Merry Christmas to all!
Dave Rooke
Circo Craft - Pointe Claire
>______________________________ Reply Separator ______________________________
> How would pumice scrub play in the formation of nodules and what
> preclean stage may you be referring to?
>
> Don Hoppe - Zycon
>
>
>______________________________ Reply Separator
_________________________________
>Subject: Re: Copper plating
>Author: [log in to unmask] at corp
>Date: 12/19/96 9:48 PM
>
>
>I would suggest looking more closely at the preclean. Is it possible that
>you are using Aluminum oxide or pumice preclean?
>
>Dave Rooke
>Circo Craft - Pointe Claire
>
>---------------------
>>We have been exhibiting miniature size nodules on our panels for quite
>>some time. These miniatue nodules resemble a slightly high brightner
>>burn.
>>I was wondering if anybody can give me a few suggestions to where I
>>should look.
>>
>>Afew test I have ran were with bare laminate through a scrubber before
>>plating. Nodules appeared on them.
>>
>>Afew more experiments were ran through different preclean lines and all
>>led to the same result, nodules.
>>
>>My questions if anybody could help are:
>>1. Would a rectifier with too high ripple affect the leveling of copper
>>plating?
>>2. We currently hot load our racks into the bath, the program is set up
>>with a five second lag and raises from 0 amp to calculated amperage. So
>>the panel sees 5 seconds of 0 amps before the rectifier applies voltage.
>>Could this be a contributor?
>>
>>Timothy Gaylor
I'll add my $20/1K to this topic.
Nodules have to propagate from something. Four of the best
things are:
1. Dirt
2. Copper
3. Palladium (especially very low leveling acid copper
baths)
4. Carbon itself
I would really take a strong hard look at the filtration for
your circulation systems (air, and solution). Are there
enough bath turns? What size filter (microns, filter area)?
NOTE: Carbon treatment can contaminate an acid copper bath
with tiny, nodule producing carbon particles which float
around until some unsuspecting PWB panel comes in contact
with them. Then they attach themselves and copper nodules
begin propagating.
Look at the circulation of your copper baths. Does the
whole bath come in contact with the filtration media a large
number of times per day? One good thing to do is to pump
the acid copper bath over to a (handy) CLEAN tank through a
fine filter, then clean out your acid copper tank, then
filter (new filters) the solution back.
Also change your anode bags for new when you do this.
Sources for particles:
DIRT:
Air, panels, people working over the tanks
COPPER:
Anodes, panels, CuSO4
PALLADIUM:
Panels (Some electroless coppers don't put enough
copper on the panel surface to cover all the palladium,
scrubbing exposes palladium)
CARBON:
Carbon filtration, is the copy machine right next to
the acid copper tank he asks tongue in cheek? You really
ought to see what that stuff does to an acid copper deposit.
I tried it when I had too much time on my hands.
Sorry for being so long winded. I hope this helps. You
might also call your acid copper supplier for some help.
Also, one of the smartest people I have ever met on acid
copper is Peter Dzioba at MacDermid. 203.575.5700
Dave Sullivan
Rockwell Collins, Inc.
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: Unidentified subject!
Author: [log in to unmask] at ccmgw1
Date: 12/20/96 10:10 AM
Timothy,
When you look at the nodules under high power or microsection do
they appear to be small/short/and round or kind stringy?
Air agitation....when was the last time you changed your blowers' filters
and are they exposed to a semi dirty area susceptible to wind?
Could you have algae growth in your brightner tank? This seems to be
fairly common.<??????>
Thoughts....
Groovy
Date: Thu, 19 Dec 1996 13:10:09 -0500
From: [log in to unmask] (Timothy Gaylor)
To: [log in to unmask]
Subject: Copper plating
Message-Id: <[log in to unmask]>
Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
Content-Transfer-Encoding: 7BIT
At first we had a few worries of contaminants in the plating baths and
we Carbon and peroxide treated one bath and no improvement. There were
a few suggestions of having fungus in the brightner lines, as it is
automatically added based on an amphour meter.
All brightner lines were changes to eliminate this possibility.
For more information about the baths:
All three acid copper baths are in the same plating line. All baths
using one hoist and is controlled by a central computer.
The nodules seem to have shown up in all three baths apporximately the
same time.
Characteristics all three baths have in common:
Same agitation speed
Central controller (computer)
All three baths are Hot loading-with a 5 second lag
We are currently using PC-606 brightner.
All chloride levels are checked and all well within the vedors specs.
Questions:
1. Can a 5 second lag for hot loading be detrimental to copper plating?
2. What results will we see on a Copper plated panel if the ripple in
the rectifier is excessive.
If you have any suggestions or need more info, please let me know.
I'll get back with you on anode to cathode distance
T. Gaylor
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