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November 2002

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 21 Nov 2002 12:01:56 -0500
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text/plain (57 lines)
I would not recommend adding flux to the paste. My experience suggests
that you will see solder balls and solder fines after the reflow
process. I sounds to me like you should manufacture those last 75 units
by installing that comonent after reflow by hand.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Hornback
> 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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