Earl,  you will notice practically all PBGAs use SMDPs on the BT laminate
(package side).  One can presume this is to improve yields during BGA
package assembly by keeping the solder balls from rolling off their pad
before attachment.

Ryan Grant

-----Original Message-----
From: Earl Moon [mailto:[log in to unmask]]
Sent: Thursday, May 23, 2002 11:05 AM
To: [log in to unmask]
Subject: Re: [TN] BGA Solderability


Totally agree with you on SMDP's. Did much work on this in earlier days and
concur about stress. Question I always ask is why, but for this situation
though not needed as such, does anyone use solder mask defined pads for
anything?

Earl

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