Thanks, Mike, Dave, Rex and Wayne. Excellent info. 

Blair


On Wed, 24 Jul 2013 09:38:14 +0100, Mike Fenner <[log in to unmask]> wrote:

>Soldering chemicals - fluxes - can be susceptible to high humidity levels.
>The sensitivity depends on the type and specific individual formulations
>within that type. The seriousness of the effect on performance change
>induced by the humidity will depend on the sensitivity of your process.
>In solder pastes high humidity can cause the flux to become more active
>leading it to react wit the solder powder reducing its (the flux)
>effectiveness on reflow and causing rheology changes leading to poor print
>performance. Generally the viscosity will rise. Water soluble materials are
>affected more than resin based materials. Additionally you may have
>increased cleaning difficult with water washable products.
>Ingress happens at the print stage effectively degrading performance there
>and all down the line. And after printing before placing.
>Whether these performance changes are significant depends on your process.
>Very fine pitch is clearly going to suffer more and sooner.
>Very low humidity can also sometimes be an issue, fortunately the optimum
>for solder paste is pretty much the same as for humans and static control.
>On wave soldering high humidity used to be a real problem when foam fluxing
>as the flux is continuously exposed to the air through the working shift.
>The increased water content would mess up the SG/solids ratio, giving
>falsely higher solids contents for a given SG. Spray fluxing clearly is not
>going to be affected in this way.
>
>Regards
>
>Mike Fenner
>Bonding Services & Products
>M: +44 [0] 7810 526 317
>T: +44 [0] 1865 522 663
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
>Sent: Tuesday, July 23, 2013 8:48 PM
>To: [log in to unmask]
>Subject: [TN] Humidity Issues
>
>Hi Technetters,
>
>Been rummaging through the archives looking for info on humidity issues in
>soldering process, found some interesting info on why keeping boards sealed
>and if not, baking, is important to preclude delimination problems. Hoever
>what I was looking for seems to elude me.
>
>Assuming that boards are stored properly and are below the levels of
>moisture content that can cuase problems, and that MSDs are also stored per
>industry standards, what other issues does humidity induce in the sctual
>soldering process itself? If the humidity gets too high, even though a
>facility has air conditioning it may only control temperature and not
>humidity level, will this cause additional problems in the process itself?
>
>Thanks,
>
>Blair
>
>
>
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