An added question regarding BGA defects...

We are in the process of designing an 8 layer polyimide board which uses a 625 
ceramic BGA.  The physical size of the component is determined by the stuff 
inside (its a MCM).  It is our intent to utilize the inner most balls as a 
thermal path for heat dissipation (the component is 9.5 watts).  In doing so, 
the three outer-most rows of balls will be used for signal, power and ground 
I/Os (this is all that is required) and the rest of the balls will be connected 
to thermal vias going down through the board (we remove the heat from the 
back).  The pads on layer 1 to which the thermal balls will be soldered to will 
be one solid copper plane (approximately .9" square).  The solder pads on the 
board in this vicinity will be defined by solder bask over bare copper.  The 
thermal vias (.9 x .9 area) will terminate at layer 8 also to a solid copper 
plane.

Does anyone feel that this design will hinder the soldering process in any way?

If so, any suggestions?

Thanks in advance,

Jim Marsico
(516) 595-5879
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