Probably, components from this first side could be desoldered by heat while you reflow solder the second side. How to do this properly?
nope. the parts' wont fall off , even if the solde rmelts.
here is how you approach this one: you do the same like what dave did but you begin by placing 2 blocks of metal or wood on the bench and taping them down. then you put two pieces of scrap board down with the board inbetween.
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= : scrap board
- : wood or metal block
I just left a small 'lip' exposed simply drop the board in
==== BBBBBBBBBBBBB====
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see how it rests at the edge on the blocks ?
then go on by placing stencil etc..
when you reflow the solder on the bottom will liquify but the cohesion forces ( is that the right term ? hmmm ) of the solder will keep the pins or pads of the parts trapped and the parts will not fall off. Even a TQFP will not fall of the board. ( unless you thump the board of course. ) let it cool down and done.