When the board is sent through the reflow oven, has it been profiled
to verify that questioned joints have reached 210  deg F?  Solder may not
completly reflow.  Does the temperature profile burn off the flux before it
reaches the reflow temp? If there is no flux at the time the solder reflows
the solder may be oxidized..
 Ramon

> -----Original Message-----
> From: Dave Hornback [SMTP:[log in to unmask]]
> Sent: Thursday, November 21, 2002 11:28 AM
> To:   [log in to unmask]
> Subject:      [TN] SMT component oxidation
>
> Hello TechNet folks, I need a little help.  We have an SMT RF duplexor
> that
> has a ~20% yield hit due to bad wetting under the component, we suspect
> they have slight oxidation.  Because it is an RF component the solder
> process must be very consistent.  On the units that fail we can remove the
> component, add a little flux, then reflow the same component back onto the
> board.  This fixes nearly all the failures.  The parts are in tape and
> reel
> and are not convenient to pre-tin.
>
> One of our mfg folks suggested we add a little liquid flux on top of the
> paste immediately after screening.  This is the last build of this
> product,
> just 75 units, so we don't want to re-engineer the entire process.  Has
> anyone tried something like this?  I'm a little nervous to introduce a
> science project at this stage.
>
> Any advice?   Thanks, Dave
>
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