On 5/27/2010 5:51 AM, N_Cook wrote:
I've only used full size hot air gun and protective masking-off before. I
prefer the short sharp shock of full size rather than the "proper" pulse jet
type things, presumably for rework only really.

Couldn't resist one in a pound shop, unbelievably precisely small spot of
flame and also adjustable (upwards), amazing engineering, minimum about 1mm
diameter.
For SM salvaging rather than just removal, any other tips from actual users?

That torch produces plenty of temperature but not nearly enough heat.

I use two hot air guns, one aimed at the back of the board and one
on the front. (The copper ground planes act as heat sinks, so you need
to pour a bunch of thermal energy into the area in question in order
to get sufficient heat rise to melt solder.)

I normally heat up the back of the board before I even start the
'front side' air gun. Two guns are more convenient than one.
Most of the time however, I can use the same gun for both.
Heat the back thoroughly and then concentrate on the front.

I dab a little solder paste in the area. That is my local
'thermometer'. When it melts, I know I'm only seconds away
from 'liftoff'.

Strip some 30 ga. wirewrap wire to route underneath BGAs.
You can form a cradle to gently lift the device off the board.


--Winston