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September 2000

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Subject:
From:
Barry Gallegos <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 6 Sep 2000 06:31:58 -0600
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I just run into this myself, however I am using Alpha 857 water soluble in a
spray application. Could this be the same issue.


Barry Gallegos, PE
Western Electronics, LLC
110 E. 43rd st. Boise, ID. 83714
P-208-377-1557
F-208-377-9836


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Franklin D Asbell
Sent: Wednesday, September 06, 2000 6:21 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Dross on PCB Assembly after wave solder


A question...you said "...solder mask may be unsuitable...this is quite a
common
problem..."

I've not heard of this before, of course I'm a fabricator, not an assembler,
but I'm
confident if our customer's were having this problem (i.e. "...this is quite
a common
problem") I'm sure they'd be screaming... Would you please expand on those
comments,
thanks.

Franklin D Asbell

Brian Ellis wrote:

> OK, Darren. It is not easy to be categorical but I suggest you are
> losing in at least one of two directions, maybe both.
>
> 1) So-called "no-clean" fluxes usually have relatively small amounts of
> activators which tend to sublime/evaporate at temperatures exceeding ca.
> 50°C. It sounds like you may simply not have enough left on the board
> when it hits the wave. Try wicking down the preheat a little at a time
> until the results improve, if this is the case. Perhaps a little more
> flux sprayed on would help, as well.
>
> 2) It may also be that your solder mask is unsuitable or incompatible
> with the flux or has been insufficiently cured. This is quite a common
> problem, especially with some of the glossy masks and dry-film types.
>
> This list is not exhaustive, but you have a 95+++% chance that the
> answer lies above.
>
> Brian
>
> Darren Goh wrote:
>
> >
> >
> > Hi,
> > I would really appreciate some help here..
> > I am running some mixed board (thru holes with SMD) over wave.. after
> > the wave, I discovered almost 80% of the boards are spatter with small
> > lumps of solder dross on the under side... (between three to five
> > counts of them)
> >
> > I am using Tamura no-clean flux and on board preheat temp is peak at
> > 100degree for 10 sec. the whole preheat zone runs at 80 sec..
> >
> > am using Alpha Metal solder bar ..and adopting spray fluxer
> > technology, no clean process..
> >
> > I hope that someone could highlight and share with me the reason (if
> > possible solution) for the formulation of solder dross on the under
> > side of mixed technology boards after wave.
> >
> > thank you very much
> > Darren
> >
> > DID:- (65) 2493448
>
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