We are designing a new PC board with a bunch of 0402 caps on the back side of a 1mm pitch BGA.  The recommended pad size for the caps is rectangular (0.63x0.64mm).  The distance between the corners of these pads and the pads around the board vias is less than 4 mils (I know I’m mixing metric and English units).  We are discussing the possibility of rounding the corners to increase the spacing, hoping to reduce the cost of the PC boards.  Another possible choice might be octagonal pads.  The extreme case of rounding the corners is making circular pads.  I’ve never seen octagonal or round pads.

Questions for the group:


  1.  Have you seen round pads used for 0402 caps?
  2.  Will properly sized round pads cause problems with 0402 caps?
  3.   If round pads would work, what is the smallest pad size to consider?
  4.  Are there other options that I may be overlooking?

Thanks,
Carl


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Carl B. Van Wormer, P.E., AE7GD
Senior Hardware Engineer
Cipher Engineering LLC
    21195 NW Evergreen Pkwy Ste 209
    Hillsboro, OR  97124-7167
    503-617-7447x303
    [log in to unmask]<mailto:[log in to unmask]>     http://cipherengineering.com<http://cipherengineering.com/>

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