I've used some QFN packages from Linear Tech, and the
contract manufacturer did hand assembly on them
(amazed me that they did...but it also had 0201 parts
as well) and found about half didn't get soldered
right.  With a magnifying scope, my tech was able to
solder these pretty easily.

My take is...if your doing 100 boards, its still
better to get a CM to flow them.


--- Bob Axtell <engineer@cotse.net> wrote:

> I've never gotten those large QFN packages to work.
> QFN8 is the largest
> I've even made work.
> 
> Lotsa luck!
> 
> --Bob
> 
> Trevor Page wrote:
> 
> >Hi list,
> >
> >I have produced a design for a small wireless
> device that uses an
> >18LF252 in a 28-pin SO package. I need to reduce
> the size of the PCB if
> >possible, and I am thinking about using an 18LF2520
> in a 6mm^2 28 pin
> >leadless QFN package. Hopefully these boards will
> be machine assembled
> >eventually, but I will initially need to be able to
> hand-solder around a
> >hundred of these boards, and so that leads me to
> the obvious question:
> >can these packages be realistically hand-soldered
> by someone who is
> >competent with working with SMT devices? 
> >
> >I notice that the QFN package has a large ground
> pad in the centre. I
> >guess that it is necessary to solder this area to
> the PCB for mechanical
> >strength, is that right? Would it be very difficult
> to solder reflow if
> >I provided a few vias underneath the device and
> used a heatgun, paste
> >etc?
> >
> >Would I be strongly advised to stick to the larger
> SO package?
> >
> >Thanks,
> >
> >Trevor.
> >
> >
> >_______________________________________________
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> >
> >  
> >
> 
> 
> -- 
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