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I'm wondering if there is some rule of thumb about how close different BGA packages can be placed to each other. What limits that besides pick and place accuracy?

I'll ask a few board assembly places for their recommendation but I was wondering what the lowest common denominator recommendation is (similar to how 6 mil trace and space is a pretty standard thing most pcb manufacturers can do without adding extra cost).

Are there any similar rules of thumb about passives near a BGA? and anything on the opposite side of the board under a BGA?

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closed as primarily opinion-based by Passerby, RoyC, laptop2d, Finbarr, PeterJ Feb 27 '18 at 14:28

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ It depends on the BGA, but in quite a few cases (especially things like microprocessors) the opposite side of the board has quite a few passive components (especially decoupling capacitors). \$\endgroup\$ – Jerry Coffin Feb 25 '18 at 6:20
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    \$\begingroup\$ If you want to possibly be able to re-work the BGA, probably 40-60 mils (with the person doing the re-work's happiness being proportional to the spacing). Otherwise I've not heard of any other special BGA constraints vs other components. \$\endgroup\$ – Zekhariah Feb 25 '18 at 7:04
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    \$\begingroup\$ This would apply also to other components, but it's worth pointing out. You should take heat dissipation and thermal flow into account. If your BGA parts dissipate lots of heat you'd have to carefully consider how spacing affects their effective thermal resistance and power handling capabilities. \$\endgroup\$ – Lorenzo Donati Feb 25 '18 at 7:08
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BGA or similar packages/technology has no special placement requirements aside from the board manufacturers minimum for trace spacing or via sizing. If you can route two bga chips next to each other based on their pinout, then there is nothing stopping them from being right next to each other. Multiple layers help this placement.

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