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I've never had to do the layout for a board involving a BGA part until now. I'm curious what the rule of thumb is on oversizing the pad for the ball. What size pad should I use if a part has balls that are .35 mm diameter with .65mm spacing between centers? Is there a general rule of thumb for how much to oversize the pad on a bga part?

Edit:

Here's a screen shot of the part from the datasheet

enter image description here

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  • \$\begingroup\$ Not too large to have enough solder mask. \$\endgroup\$ Jan 29, 2014 at 6:13
  • \$\begingroup\$ Can you clarify? I saw on this page: eevblog.com/forum/eda/… that the recommended pad size is actually smaller than the nominal ball size. About half way down somebody states .6x. \$\endgroup\$
    – Doov
    Jan 29, 2014 at 9:14
  • \$\begingroup\$ The land is usually smaller than the ball on a BGA of that pitch or coarser. Maybe 0.29mm. I use the IPC-compliant wizard on EDA software, which uses a lot more information than you've given, so this is not an accurate answer. \$\endgroup\$ Jan 29, 2014 at 13:01
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    \$\begingroup\$ The IC manufacturer has "no recommendations." I'm trying to see if I can get this done using oshpark's service which has 5/5 trace space and 10 mil drill min with 4 mil annular ring min. \$\endgroup\$
    – Doov
    Jan 29, 2014 at 18:21
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    \$\begingroup\$ @TomCarpenter you and me both. It's an imaging sensor from Aptina. Their documentation leaves much to be desired. \$\endgroup\$
    – Doov
    Jul 29, 2015 at 16:52

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Intel's BGA packaging guide has some good guidelines:

http://www.intel.com/content/dam/www/public/us/en/documents/packaging-databooks/packaging-chapter-14-databook.pdf

Check out pages 17 through 20.

They recommend a 20 mil pad with a 24 mil mask opening, for 2mil annular ring.

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