Thanks anyway. Has always seemed like Rudy has a great fund of knowledge. I may check back with you after talking with the process people.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Chuck Brummer
Sent: Friday, September 11, 2009 1:37 PM
To: [log in to unmask]
Subject: Re: [TN] tin redeposit???
Louis,
I knew I should have kept my big keyboard shut until Rudy chimed in. He
always has a better answer then mine on chemical questions.
have a good weekend,
Chuck Brummer
3M Manufacturing Engineer
8357 Canoga Ave.
Canoga Park, CA 91304-2605
(818) 734-4930
From:
R Sedlak <[log in to unmask]>
To:
[log in to unmask]
Date:
09/11/2009 10:28 AM
Subject:
Re: [TN] tin redeposit???
Sent by:
TechNet <[log in to unmask]>
Louis:
This is a very common problem, particularly if you are stripping in a
tank.
There exists a mechanism to completely stop this, which is available in
some strippers, like ours for instance.
Other things you can do to minimize the problem, over time:
The current Tin plating baths usually have a high load of (Stannic) Tin
oxide dispersed in the bath. This is the enemy. This oxide is
co-deposited with the metal, then dissolves in the stripper, and immersion
plates on the exposed Copper.
Put a VERY fine filter on the bath, to filter out the Tin oxide. Monitor
dissolved Tin oxide levels by taking a 250 ml cylinder of bath out once a
week, and allowing to settle overnight, and noting level of settled oxide.
Make sure anode area is high. Too low an anode area promotes the Tin
going to Stannic Tin oxide, instead of going into solution as Stannous, as
it "should".
Further info on photoresist strippers that prevent this problem available
off-Technet.
Rudy Sedlak
RD Chemical Company
--- On Fri, 9/11/09, Louis Hart <[log in to unmask]> wrote:
From: Louis Hart <[log in to unmask]>
Subject: [TN] tin redeposit???
To: [log in to unmask]
Date: Friday, September 11, 2009, 8:57 AM
Technetters, hoping this question is not too arcane, has anyone
experienced sporadic tin redeposit on exposed copper surfaces during the
photoresist stripping process prior to final ammoniacal etching? In this
case electroplated tin is used as an etch resist.
Thanks for any comments.
Louis Hart
Compunetics
Monroeville, PA
USA
[log in to unmask]<mailto:[log in to unmask]>
412-858-1272
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