JW wrote in
:

On Tue, 30 Oct 2007 02:19:53 GMT "James Sweet"
wrote in Message id:
dxwVi.4781$8R1.1562@trndny02:


"Jim Yanik" wrote in message
. ..
"James Sweet" wrote in
news:8IeVi.4547$8R1.585@trndny02:




You don't spray anything *under* a BGA, just a quick shot on top
does the trick.

If you have a bad solder joint under a BGA,how do you "fix" it?


Generally you don't, but you know to stop screwing around looking for
the problem elsewhere.

It may be possible to fix with a heat gun as a last ditch effort, but
that really could do further damage.

I've had some success reflowing BGAs that have fractured or poor
solder joints around their perimeter using a Hako 850 and a small
nozzle which allows me to concentrate the air just where it's needed.


it seems that the only reliable way would be to remove the BGA chip and
somehow put new solder balls and flux on all the PCB pads,then reinstall
the BGA and reflow using a preheat hot plate and hot air gun.
Never tried it,though.

--
Jim Yanik
jyanik
at
kua.net