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| Date: | Mon, 9 Apr 2007 09:18:37 -0400 |
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If you look at the original Bellcore (now Telcordia) documents you find
that one of the worse things you can do for mixed technology PCBAs is to
use rosin based solder pastes for surface mount and then use water
soluble flux and aqueous clean for wave soldering. Bellcore GR78 Core
has a set of procedures for determining if a rosin based flux is
"compliant" (i.e., compliant to their requirments). Bellcore liked
compliant rosin based fluxes because they were not a reliability issue
if left behind. In fact, reliability was usually improved by leaving
them behind in that they trapped ionic material so it wouldn't be mobile
and they also coated the PCB surface with an insulating rosin keeping
water off the traces.
Regards,
George
George M. Wenger
Senior Principle FMA / Reliability Engineer
Wireless network Solutions
Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531
[log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Monday, April 09, 2007 9:08 AM
To: [log in to unmask]
Subject: [TN] Cleaning rosin flux with DI water..
Anyone have data as to what can happen if you remove (should actually
say ATTEMPT to remove) rosin flux residues with DI water?
Long story short, we buy a transformer that the mfr told me is soldered
with rosin, medium activity flux. Their cleaning process is "scrape
flux residues with a knife"....enough said about that... We solder with
organic high activity and clean with DI water. Guess what - return from
field with fire on the pcb...burned out a trace through the PCB under
the power pin of the transformer. Since learning of the above info, I
am inclined to think maybe the rosin residue could have trapped water or
OR flux / flux residues and created a nice little corrosion spot.
Anyone have opinions or experience on what can happen if you try to
clean the "no clean" with just water?
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