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September 2003

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 12 Sep 2003 12:01:47 +0300
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Paul has hit it on the head. Particularly with solder pastes, they
mostly absorb humidity like a sponge and this affects the printing, as
well as the soldering. Keep stencil open times as short as possible.
With liquid fluxes, the effect should be less remarkable but if you use
an air driven spray fluxer or a foam fluxer, the extra humidity in the
air, especially if compressed, could certainly effect alcohol-based
"no-clean" fluxes.

Brian

Howard Watson wrote:
>
> Hi all,
>
> There is a presumption (not supported with data) here that when it
> rains, and the humidity goes up, we historically have experienced more
> solder defects.  I realize that humidity can affect MSD's and PCB's, but
> what, if any, would be the symptom of high humidity, in terms of solder
> joint defects at wave and reflow (solder balls,voids)?  Our process is
> strictly no-clean.  Normally, the humidity in our plant is 10-30%, and
> when it is high, it's in the 50-60% range, which is probably not even
> that high compared to some of your plants located in humid climates.  I
> suspect that our problem may be something other than the humidity.
>
> Also, we don't bake our PCB's, and I'm not sure if it's necessary.
>
> Howard Watson
> SMT Manufacturing Engineer
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