iMX8M Nano -- What are these holes in the PCB for?

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iMX8M Nano -- What are these holes in the PCB for?

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jaredwheeler
Contributor II

In the EVK SoM board for the 8M nano, the processor is surrounded by 6 unplated holes drilled thru the PCB.  I've attached a screen grab of these holes in a PCB layout.

Can anyone shed some light on the purpose of these holes?  Are they for EMC? Are they used during manufacture?  What parameters govern their effectiveness? 

Any help with vocabulary or pointers to documentation about these would be helpful!

Thanks!

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jaredwheeler
Contributor II

Thanks for the replies, folks.  I’ve found the purpose for these.  They aren’t holes at all, I was just mis-reading the PCB layout files.  

They’re local component PCB fiducials.  Used by the vision system on the PCB assembly pick and place machine to accurately position the 0.5 mm BGA pitch 8M processor.

The size and layout requirements are defined by the vision system in use at the PCB fab.  So when designing your own PCB layout, you have to contact the assembly engineering staff at your PCB fab to get the specifics.

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jaredwheeler
Contributor II

Thanks for the replies, folks.  I’ve found the purpose for these.  They aren’t holes at all, I was just mis-reading the PCB layout files.  

They’re local component PCB fiducials.  Used by the vision system on the PCB assembly pick and place machine to accurately position the 0.5 mm BGA pitch 8M processor.

The size and layout requirements are defined by the vision system in use at the PCB fab.  So when designing your own PCB layout, you have to contact the assembly engineering staff at your PCB fab to get the specifics.

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carotte
Contributor III

Thats wrong.

They are holes indeed...

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jaredwheeler
Contributor II

Yeah, you’re clearly right about that.  Not able to unmark my incorrect fiducial solution post.

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carotte
Contributor III

My guess is, that the four big ones were intended for mounting a heatsink. 

Definitively not for EMC.

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b45499
NXP TechSupport
NXP TechSupport

Are you using NXP reference board? Or the third company design board?

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