Peter & Gordon,
If you have unactivated flux left after Wave Solder processing, are you not
maybe using a bit too much flux? Also the fact that you're using a hot air
rework station to activate the flux until it disappears means that you are
subjecting your boards to unnecessary thermal excursions that will
ultimately reduce the life of the board. Either that, or you're not using
the correct temperatures to activate the flux in the first place.
Just an unsolicited and gratuitous 2c's-worth.
Peter
Gordon McAlpine <[log in to unmask]> 20/09/2002 06:46 PM
Sent by: TechNet <[log in to unmask]>
Please respond to gordon.mcalpine
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] Noclean Wave soldering
We currently use a no-clean process {no wash process} with our assemblies
and have
had the following issues to contend with.
1} Unactivated no-clean flux leaves a white residue on the board. Although
this is non-
corrosive it is unsightly to the customer. We have been using a hot-air
rework station to
remove this residue by activating the flux till it disapperars.
2} We did try at one point to try and clean the boards with a cleaner
"prozone" but this
is not recommended. The reaction between the flux and the prozone caused
the areas
applied to become hydoscopic and absorb moisture. The boards then started
to "grow"
a white residue almost powder like growth.
3} On hand soldering of parts after wave solder, we used to use the same
flux that was
in the solder bath, but although the board looks clean immediately after
the sodlering
process, if it is left for approx 24hours then this unactivated flux
residue appears. We
combat this by only using a rework gel flux for apply to the board before
hand soldering.
Hope this helps...
On 19 Sep 2002 at 23:10, Peter Lee wrote:
Date sent: Thu, 19 Sep 2002 23:10:26 -0700
Send reply to: "TechNet E-Mail Forum." <[log in to unmask]>,
Peter Lee <[log in to unmask]>
From: Peter Lee <[log in to unmask]>
Subject: [TN] Noclean Wave soldering
To: [log in to unmask]
> Technet,
>
> Is anyone currently adopting a no clean flux/ no post wash with their
> Wave soldering process? We had a few wave soldered products requiring
> post hand soldering due to non-washable components (filters,
> transformers etc.)
>
> In particular, I like to know what areas of concern you run into (eg.
> Remaining Flux residues, conformal coating) and your feedback on the
> overall cleanliness of the boards.
>
>
> Rgds,
> Peter
>
>
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---------------------------------------------------------------------------------
Best Regards
Gordon McAlpine
Test Engineering Manager
Telspec Scotland Ltd
Tel :- 01738 494500
DDI :- 01738 494506
Fax :- 01738-630012
E-Mail :- [log in to unmask]
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