The difference between a flux and an acid clean is that the flux will
prevent re-oxidation during the soldering process, whereas the acid will
likely be dissipated on heating. Hot copper oxidises.
The acid etch will bring the copper to a consistent high standard of
cleanliness (this could vary according to prior processes, standing times
etc), making subsequent processes consistent.
The reduced oxide burden means the flux can then be of a lower chemical
activity and this will simplify post solder cleaning to achieve the very low
residual ionics needed
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
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Indium Corporation
Incorporated in New York, USA
Registered office: (Not for correspondence)
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----- Original Message -----
From: "Louis Hart"
To:
Sent: Friday, March 21, 2008 10:20 AM
Subject: [TN] preparation for HASL
TechNetters, a question has come up in our plant about cleaning copper
surfaces before HASL. (Solder used is the standard tin-lead.) We've been
putting panels through a light acid clean and etch, then through a
Quicksilver flux applicator with two rollers that appear to be saturated
with Enthone 757 SG flux. Someone has asked if that acid clean and etch are
really necessary, since what is flux supposed to do?
Any comments on the need for the acid clean and etch would be most welcome.
Many thanks - Louis
Louis Hart
Compunetics
Monroeville, PA
USA
[log in to unmask]
412-858-1272
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