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February 2000

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Subject:
From:
Murugan Vasudevan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 15 Feb 2000 08:21:08 -0800
Content-Type:
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text/plain (132 lines)
Thanks for the quick reply Jorge. Glad to know that
you guys have done this before. Continuiing on the
topic a little more, our case here is that of double
sided reflow - with the components that have to be
reflowed on the bottom and those to be cured on the
top side as the board goes into the forced convection
oven. The chief concerns here with some of the process
engineers are one of chemical interactions between the
glue and the solder paste. Whether there might be any
outgassing from either one of the materials that might
affect the cure/solderability and the future
performance of the other material.
I am kinda wondering how to set-up and study this
phenomena (if at all it exists!).

Any ideas floating around??

Regards,
Murugan


--- Jorge Engenharia <[log in to unmask]> wrote:
>   Murugan;
>
>   I did this in the past to avoid 0603 tombstoning
> during reflow until new
> land size was modified in the board. It worked well
> !!!
>   First we applied solder paste using screen printer
> and then we applied
> glue using a syringe dispense equipment ( Panasonic
> ) using a double dot
> pattern nozzle, this process requires continuos
> monitoring due some times
> you get the nozzle dirt with solder paste. We did
> this in 1994 when a new
> board design was made using 0603 and nobody realize
> that tombstone could
> happen, that time 0603 were a new component for us
> and until we get the
> problem fixed by changing land pattern design and
> solder paste ( we did a
> small DOE study ), we had to apply adhesive to avoid
> tombstone and keep
> production running ( 10000 boards per day !!! )
>   The adhesive used were Loctite 3605 ( I am not
> sure about the number, but
> it were red and came in 20 ml syringe package ) and
> the reflow profile were
> the same that I used for solder paste.
>   I believe this process is used also for double
> sided reflow with heavy
> components on both sides.
>
> Thanks
> Jorge Dourado de Santana
> Maintenance / Process Engr
> Microtec - Brazil
>
>
> > -----Original Message-----
> > From:       Murugan Vasudevan [SMTP:[log in to unmask]]
> > Sent:       15 de Fevereiro de 2000 12:24
> > To: [log in to unmask]
> > Subject:    [TN] Cure and Reflow
> >
> > Hi Technetters,
> >
> > Just wondering if anyone of you have done
> simultaneous
> > cure of SMD adhesives and reflow of solder paste
> in
> > the same pass. Any information/leads on any
> previous
> > experiences with this process will be very
> helpful.
> >
> > Thanks,
> >
> > Murugan.
> > __________________________________________________
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