Hi Julie - I don't know of any standards that cover this topic unless 
there is something in the IPC-7711 specification. When we use our BGA 
repair procedure, we use specific fluxes that are easily removed and we 
are very conscious about the volume of flux used. "Bigger the glob, better 
the job" is not a applicable process philosophy when utilizing fluxes for 
BGA repair. Our focus for the process is to insure that we are using flux 
in such a way that we don't cause a reliability issue that was not there 
prior to our BGA repair actions. The example we discussed of the flux 
packed under the BGA in the previous Technet thread is a classic case of 
not understanding how much flux was necessary for successful BGA repair.

Dave Hillman
Rockwell Collins
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From:   Julie Silk <[log in to unmask]>
To:     <[log in to unmask]>
Date:   11/13/2012 07:51 AM
Subject:        [TN] Reflux and reflow BGA rework
Sent by:        TechNet <[log in to unmask]>



A discussion of the practice of re-flux and reflow of BGAs to rework them 
has emerged within the "limits of flux residue" discussion.  I'm taking it 
out into a separate thread.  This rework process injects flux under the 
BGA, then reflows the BGA.  The part is not removed.  It will frequently 
make a part that wasn't working work again.  The heat damage to the board 
is less (fewer cycles) than a replacement process.  The question Joyce 
asked about whether there are standards and reliability studies has not 
been answered.  What is the proper procedure for this rework process?  Are 
there official standards?  Studies of effectiveness / reliability?




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