Hi, Peter,

We use 35mm BGA's on our boards and have not had a problem with them, even
when replacing them. The fact that you're getting bridging at the corners
and seeing some warpage are probably not separate subjects. My two main
suggestions are: (1) bake out the components per IPC spec (48 hours at 125
deg C) to be sure they're dry, and (2) use flux paste only to replace them
- do not use solder paste.

Good luck!
Peter



Peter Lee <[log in to unmask]>  10/09/2002 04:16 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Peter Lee

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: [TN] BGA rework - excessive collapsing








Technet,

We are having problems replacing 35mm BGA, 1.27mm pitch on a OK industry
BGA rework station. The resulting X-ray revealed a solder bridge at one
corner.

There was some warpage on the BGA but not significant. PCB was
reasonably flat. Thermal profiling was done to ensure all temp. were
optimum. I did notice the BGA balls collapsing quite a bit (at least
half of the ball height) after rework.

Anyone has suggestion on how to minimize the chance of bridging? Is it
common for BGA of this size? We don't have the capability to paste the
board for BGA rework.

Rgds,
Peter

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