Toni,
I would like to add to the good comments from Richard and Susan.

The third thing you can do is check to see that your preheat is high enough
to drive off all the solvent of your flux before it hits the wave.  If it
doesn't, what you may be seeing is the relatively explosive evaporation of
the remaining solvent when it hits the molten metal wave.

Also, typical alcohol based fluxes have about 0.15% water content, but if
your plant is not air-conditioned or the humidity just over whelms the
system your flux can start to take up water from the atmosphere as water and
isopropyl alcohol are "cousins" (like dissolves like).  % water levels can
go quite high and I have seen problems starting at 1.5% and real nasty
problems at 2%.  Obviously this really only applies to wave, foam and drum
spray fluxing.  More modern spray fluxes do not have this problem as the
container is closed and the flux is not recaptured once it is dispensed.

good luck,
Bev Christian
Manager, Materials Engineering Lab
Nortel

> ----------
> From:         [log in to unmask][SMTP:[log in to unmask]]
> Sent:         Saturday, June 13, 1998 6:24 AM
> To:   [log in to unmask]
> Subject:      [TN] Outgassing problem in pcb's soldering
>
> Dear Sir /Mme:
>
> My name is Toni Casas and I'm working as a quality engineer in an
> entreprise
> which performs electronic circuits and devices for industrial aplications.
>
> I have heard about your organization and I'm sending you this e-mail in
> order to ask some things about soldering processes. I explain a little
> about
> our productive process.
>
> First of all we perform SMD assembly. Then we mount conventional
> components
> by hand and then the pcb's are soldered in a new technology soldering
> line.
>
> We have problems, especially in large pcb's, by the humidity of the pcb
> amb
> the problem known by the name of outgassing. You know, we enter the pcb
> into
> the soldering line and when the tin reaches any pad of the pcb, then it
> explodes by the presence of humidity. Our pcb's supplier says that is the
> outgassing problem, but we know nothing about that: Nothing about
> outgassing, and nothing about how to use pcb's properly to get a good
> solder.
>
> If you have any information about that, I please ask you to send it at the
> address
>
> [log in to unmask]
>
> which is my personal address.
>
> Toni Casas Pujadas
> Quality Enginner
>
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