Ramsey,
Just to play devil's advocate here, can you consider changing over to
no-clean?

regards,
Bev Christian
Nortel Networks

> -----Original Message-----
> From: Ramsey's [SMTP:[log in to unmask]]
> Sent: Friday, November 05, 1999 7:35 PM
> To:   [log in to unmask]
> Subject:      [TN] White residue on SMT after vapor cleaning
>
> A few weeks ago I wrote asking for help on with a white residue problem.
> Some technetters ask for a follow-up. Here it is.
> Case: White residue appears on ref lowed SMT land patterns after
> exposure to vapor cleaning. No white residue appears on wave soldered
> land patterns. Even on mixed technology boards.
> RMA type paste for SMT. Synthetic Activated flux applied as foam at
> solder wave.
> Vapor cleaner loaded with Vertrel XMS Plus (HFC, Trans Diclor, and
> alcohol). Ultra sonic scrub rinse.
> Prior to exposure to vapor process the flux residue is very thin clear
> and almost invisible. After cleaning the residue appears as a white
> powder where ever there was flux.
> We tried a co-solvent Axerel 32 in the boil sump, with board immersion
> instead of vapor cleaning. Rinse in Vertrel distillate with Ultrasonic
> scrub. Slight improvement.
>
> Result: We discovered that the residue was flux activators, not rosin.
> We experimented with a few flux formulation until we found an old Alpha
> Metals paste formulation that cleaned beautifully in the co-solvent
> process. 40% Axerel 32 by volume in the boil sump. We have not found an
> RMA paste that will clean completely in the traditional vapor process
> with Vertrel XMS.
>
> Did anyone ever hear of an SA solder paste formulation?
>
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