On Sat, 21 Nov 2009 09:16:59 -0000, "N_Cook"
wrote:

Is there a technique of pulling a hot ni-chrome wire under the chip,
combined with a lift/wedge/hook , so no lifting of fine board traces with
the chip ? Also no heat damage to the original chip, if a BGA solder problem
in the first place

No, or rather not that I know of. The wire would need to be VERY thin
for this to work. It would also take forever as the heat affected
zone and thermal mass of the nichrome wire is rather small. I would
think it would just smear the solder ball rather than reflow it. Some
of onine BGA repair videos suggest using glue to position the BGA
chip, which might block the hot wire.

If you're thinking of using this for repair (rather than replacement)
of BGA chips, I think you're using the wrong approach. For repair,
your trying to reconnect very small number of connections out of
possibly 100 or more connections. The idea is to fix the few, without
affecting the good connections. However, a hot wire will seriously
affect the good connections, as well as the bad. It might be useful
for removing the BGA, but not reworking it. Then, you still have the
problem of how to successfully solder the replacement chip, where the
nichrome wire method will be of no help.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558