I've soldered a variety of smaller boards in an oven without any temperature control, just a stopwatch/eyeballing the solder with near 100 percent success (I got distracted a couple of times and smoked the boards). I've soldered 0.5mm qfps with no problems.

I use paper stencils lasercut from repositionable postal labels. It helps to have a lasercutter. I adjust the stencil holes usually to be pretty small. The size relates to the thickness of the label material and the size of the pad. For qfp leads, I just cut a 1mm or so slot the length of the entire side of the chip; when melted, the solder pulls into the pads perfectly.

Paper stencils are perfect for prototyping - it takes a minute to cut a new one, and they peel off leaving a perfect pattern.

A couple of years ago I tried to solder with the lasercutter. By drawing a back-and-forth pattern it's possible to keep the laser over a pad long enough to transfer sufficient energy to melt solder (it helps to have darker solder paste). It actually worked but took too long to bother. The oven is much faster.

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

!! Is that a commercial, hobby level of lasercutter?

The lasercutter is a 30-watt Epilog.

For paper stencils, anything will do. I think even a dvd burner laser will cut paper if focused correctly.

For soldering, you need wattage. 100W would probably be good enough to do real jobs. Of you can't do BGA with a laser....

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

Isn't solder kinda reflective? So if you point a laser beam into solder won't it only reflect and burn something random in the room?

Yes, solder is a bit reflective. That's why it takes 10 seconds or so of buzzing over it with a laser, even for a small pad.

The lazer won't burn anything - it needs to be really focused, and reflecting off a drop of solder won't do. Although I do have a nasty black dot in my remaining eye...

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Not entirely joking. I recently noticed a tiny elongated black dot slightly away from focus point, especially visible when looking at a uniformly lit computer screen... Looks like a little ant. I wonder if I did somehow zap my right eye with the laser... The lasercutter housing is shielded and the smoky lucite cover should block the radiation from reflective surfaces... I did mess around with a re-housed DVD burner laser a few years ago and could have zapped myself with that... Or it could be unrelated.

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

First time that i hear about dead pixels(rods and cones) in somebody's eye. Lets hope that the nervous system will generate a patch.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

The dead spot is pretty big, and the brain will usually fill it in. Mine is unfortunately a black dot. I will probably be blind or dead before my brain 'repairs' the hole.

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In theory, there is no difference between theory and practice. In practice, there is. ...Jan van de Snepscheut

Actually, the brain can do an amazing job of patching even large holes. Oliver Sacks writes about it from experience: the brain will even fill in brickwork or carpet patterns! But it takes a few seconds - filling in from the edge.