If the pad comes off it is because there is a crack between the pad and the
base material, and no conductor is there to prevent it from coming off. I
would suspect that if you do a cross section of active pads in the same area
you have a fair chance to see such cracks unde the pads, and even lifted
pads.
You intend to  replace the BGA on this area. Are you sure that the new
connections will be as good as new?
Gaby
----- Original Message -----
From: "bob wettermann" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 17, 2006 6:10 PM
Subject: [TN] One solder Ball Not Connected on a No Connect Pad After Rework


> This question to the group is about expected solder joint strength on a
> BGA.
>
>  The BGA in question is a 8 x 8mm plastic package  BGA using a LF  SAC305
> soldering process. It has 64  x 0.018" balls holding it to  the PCB.
>
>  When removing this device for rework 3-4% of the time one of the corner
> NO CONNECT pads comes off.
>
>  The question is if we do nothing upon replacement of  a new device  to
> the damaged pad will it really make a difference ??? We are arguing  that
> the holding strength of the reworked device would be approximately  the
> same because the change in overall surface area is marginally  impacted.
>
>
>  Thanks
>
>  Bob Wettermann
>
>
> Bob Wettermann
>
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