Re: gEDA-user: OT: soldering QFN packages with exposed bottom pad?

[Gabriel Paubert <paubert@xxxxxxx>]

On Tue, Apr 28, 2009 at 02:56:07PM -0500, John Griessen wrote:
> DJ Delorie wrote:
> >>   I would think that mounting the chip upside down 
> .
> .
> .
>   I suppose you could hand-solder some copper foil or
> > desolder braid to the pad, as long as you're careful to not short the
> > pins.
> 
> 
> Then it would look like a dead, gutted bug.
> 
> I'm going to look into methods of dealing with BGAs in prototypes
> since Bill's tech says they're less trouble after a learning curve.
> 
> I've heard and can imagine the way they pull themselves to alignment
> by surface tension between the grid of chip balls and the grid of lands on the pcb.

Yes, but it works much better with leaded solder.

I've got a small reflow oven at work and I've seen 0603 capacitors 
and resitors center themselves. With a BGA, it will be hundreds of 
points pulling themselves into alignment. But I don't see how you
are going to put the solder paste without a stencil.

	Gabriel


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