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Reply To: | TechNet E-Mail Forum. |
Date: | Fri, 22 Nov 2002 08:05:41 +0800 |
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I have come across this sort of component, and it's impossible to solder
them on by hand - the plates underneath are not accessible to maunal
soldering. If you're getting a 20% failure rate, the time and cost of
removing failures, refluxing and reflowing may not be any different from
pre-tinning all the components and hand placing them just before reflow.
This would certainly save you from having to reflow them a second time.
Is your solder paste nice and new?
2 cents for a Friday.
Peter
Guy Ramsey <[log in to unmask]> 22/11/2002 01:01 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to Guy Ramsey
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] SMT component oxidation
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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