Hi.
At one of mi previous work places, we used a similar process for selective soldering.
Some of our products had QFP components on both sides of the board, and many connectors
from the top side. Hand soldering would be to long on big volume production, so we
developed the selective soldering process for this products.

What this process implies is that within the same side of the pcb, a linear section was
populated with QFP's and chip components, while THT components as well as any waveable
chip components would be aligned on the rest of the unit. The QFP's would be reflowed
and the rest would be solder waved.

To maximize production, we installed a glue dispenser right after the solder paste
printer. With the stencil we would print only the ic's and any components lined up in
the same path, then the glue dispenser would do all of the pcb (small soldered
components would be glued as well). The S.M. placement machines would do a full
population then the unit would be reflowed.
We used a glue Epoxy (Loctite) with a high curing temperature so that the profile meant
for solder reflow would not deteriorate the glue properties and still do a proper
bonding.
During waving, a masking jig was applied to the wave so the solder would flow only on
the desired paths.

We never had any problems with this particular process.

I hope this helps.







Murugan Vasudevan wrote:

> 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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