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March 2005

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Subject:
From:
Jason Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jason Gregory <[log in to unmask]>
Date:
Wed, 9 Mar 2005 14:55:54 -0600
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Hello all,

We have some boards that I am requiring some advice on cleaning residues.

The PCBs were soldered with SN96 (Sn96.5/Ag3.5). The first pass of the
boards look great. However, the second pass looked very suspicious. We are
seeing residue that looks like dried, puddled flux residue around most of
the leads. The areas mostly affected are multi-leaded components and there
is no evidence of this residue in open (non-populated) areas of the board.
If we take something like a probe or tweezers and move them along the areas
of concern, then it flakes off, but not real easily. I am afraid to do this
in fear of damaging the laminate (these are expensive boards). We have tried
re-fluxing them with aggressive RMA flux and re-reflowing them, but to no
avail. I have just tried soaking them, for 15 minutes,  in a 50/50 solution
of distilled white vinegar and DI water, but again, to no avail.

Does anyone have any suggestions as to something else to use that's
aggressive, but not damaging to polyimide (or the solder joints)?

TIA,

Jason Gregory
Manufacturing Engineer
Innova Electronics
(281)653-5593
(281)653-5594 fax
(281)212-0844 cell
[log in to unmask]

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