On Wed, 22 Nov 2006 09:56:21 -0800, Shawn Wilton wrote:
> I've had no problem doing 0603 components reliably.  It gets
> difficult when you try QFN parts.  Those require a stencil and must
> be reflowed, or put the heat gun to them.  Something I've found
> that works for me is pre-tinning the pads on the board so you can
> apply the part, put heat to the pin and it should wick the solder
> up the pin giving you a satisfactory joint.

If you know you're going to hand solder the QFN parts, it helps a lot
to make the pads extend beyond the body an extra 0.02 to 0.025" in
your PCB layout. It gives you more pad to hit with a very small tip
when soldering.

One other trick that works is to use 2 or 4 vias in the center "power
pad" of the device. Solder the pins as you normally would and then
solder the pad from the back side of the PCB. This only works if the
vias are not connected to an internal ground plane, then you'd have
to reflow them to get sufficient heating to solder the pad.

I've also had really good luck soldering small prototype PCBs in my
SMD "reflow skillet". It works really well for QFN packages. If you don't
know what the SMD reflow skillet  is all about, you can check it out at:

http://www.sparkfun.com/commerce/present.php?p=Reflow%20Skillet

Matt Pobursky
Maximum Performance Systems




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