I did just this with some standard FR-4 boards, and the lead-free
flipchips soldered up just fine. But at 235 Deg. C. some of the boards
delaminated in spite of a 24 hour bake just prior to assembly and
reflow. 
We went to a different circuit board material from North Texas Circuits
(NT) and then they worked perfectly. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phillip Bavaro
Sent: Friday, November 11, 2005 12:15 PM
To: [log in to unmask]
Subject: Re: [TN] Lead Free BGA rework

Hi Gus,

Sure, it can be done but that is a lot of work when you could just use
the lead free BGA as is and raise your reflow profile to 230-235?  Sure,
it does raise the question whether or not the other parts on the board
can handle the slightly higher reflow condition, but this intermediate
process has been used quite a bit already.

Hope this helps,

Phil





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