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February 2002

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 19 Feb 2002 13:28:10 -0500
Content-Type:
text/plain
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text/plain (127 lines)
Have you considered temporary spot mask? It works okay for chip resistors
and capacitors, SOT. Not too good for SOIC, stuff gets stuck under the
little legs.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of makshuwing
> Sent: Tuesday, February 19, 2002 6:18 AM
> To: [log in to unmask]
> Subject: Re: [TN] High temperature solder wire
>
>
> Hello eter,
>
> Adhesive dispensing, chip placement, reflow(glue curing), manual
> insertion, then wave soldering are our normal processes. After
> reflow we sometimes find some mis-aligned chips or missing
> components. The area of glue in contact with the surface of the
> mis-aligned chip could be less than normal and the adhesion force
> is insufficient to protect the chip from dropping off  during
> wave soldering. Therefore we  want to use high temp solder to
> solder the mis-aligned chips prior to wave soldering. We know
> that we could detach the parts after reflow and hand solder the
> parts after the wave soldering but we think adding hi-temp solder
> is the simpliest way since there is no detachment process is involved.
>
> Eric
> ----- Original Message -----
> From: "Peter Barton" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Tuesday, February 19, 2002 12:41 AM
> Subject: Re: [TN] High temperature solder wire
>
>
> > If you are going to the trouble to hand solder these parts on
> why not fit
> > them after the wave solder process and just tack them on,
> applying a dab of
> > rework flux first, then reflowing the solder that will be present on the
> > pads? Saves the difficulty of using high temp solder pre-wave, and quite
> > likely excessive solder on the joints post wave (the solder in your bath
> > will wet to the high temp. joints already made).  I have seen a similar
> > problem when tack soldering large multi way connectors with high temp.
> > solder pre-wave.
> >
> > Regards,
> >
> > Peter Barton
> >
> > ===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at
> > 18/02/02 13:40
> > >Hi all,
> > >
> > >We are currently using adhesive to glue chips on PCB and then
> run the board on reflow oven
> > followed by wave soldering. After the reflow process we need to
> rework some
> > chips occasionally due to chip miss-alignment or missing. To do
> the rework
> > we have to remove the original glue, re-glue the chips and let
> the board go
> > through the reflow process again. Now we want to eliminate this loop by
> > using hi-temp solder wire (melting point 268-302 degree C) to solder the
> > reworked chips without adhesive, then let the reworked board
> directly go to
> > wave soldering with solder pot temperature around 245 degree C.
> > >
> > >Has anyone using this method seen problems?
> > >
> > >Eric
> >
> >
> > -----------------------------------------------------------------------
> > Peter Barton
> >
> > ACW Technology Ltd
> > Dinas Isaf West
> > Tonypandy
> > Mid Glamorgan. CF40 1XX  Wales
> >
> > Tel: 01443 425200                       Fax:  01443 436882
> >
> > International Tel :  +44 1443 425200    Fax : +44 1443 436882
> >
> > E-mail: [log in to unmask]     Website/URL:  www.acw.co.uk
> >
> >
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