On 5/27/2010 7:42 AM, N_Cook wrote:

(...)

I don't often meet ground planes but if I do ,
how do you gauge the rear heat ?

I have not been measuring the temperature at all.
I've been relying on experience to know that I've heated up the back
side of the board 'sufficiently' but not so much as to loosen
components.

I've been eyeing these Tempilstiks to get a better idea:
http://www.use-enco.com/CGI/INPDFF?P...PARTPG=INLMK32

One could mark the board with three crayons of increasing
melting temperature and get a better idea when to start
pulling on the BGA.


I like the solder paste indicator.

It works 'better than nothing'.
Of course the virgin solder melts at a much lower temperature
than does the used solder.

--Winston