Hi Steve - take a look at the following paper:

"Ball Grid Array, MicroBGA, Chip Scale Packaging, and 0.4mm  Ultra Fine
Pitch Implementation At US Robotics", author Ron Evans, et al, pages
141-163, SMTA National Symposium "Emerging Technologies" Proceedings,
October 1997"

The paper contains some good information on ball grid array pad design and
manufacturing interaction issues that may be relevant to your issues. Good
Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





"Joy, Stephen C" <[log in to unmask]> on 06/16/98 11:33:00 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to "Joy, Stephen C" <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  [TN] Solder mask profile information




     We have been having some problems with a BGA device where we see
     ball fatigue (solder ball cracks) after temp cycling. We think it
     may be related to severe undercut of the solder mask.

     Does anyone have information on different solder mask foot
     profiles? How difficult is it to get a straight sidewall on
     solder masks?

     Are there any that are much better than others for this
     attribute? What would be the trade offs?

     You can contact me off line if you prefer.

     Steve Joy
     503-696-2239
     [log in to unmask]

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