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SMARC T335x Carrier Board Hardware Design Guide, Document Revision 1.2
4.6 Module and Carrier Board Mounting Holes – GND
Connection
It shall
be possible to tie all Module and Carrier board mounting holes to GND.
The holes should
be tied directly to the GND planes, although Module and
Carrier designers may
optionally make the mounting hole GND connections
through passive parts, allowing the mounting holes to be isolated from GND if
they feel it necessary.
4.7 Carrier Board Standoffs
Figure 49: Screw Fixation
Standoffs secured to the Carrier board are expected. The standoffs are to be
used with M2.5 hardware. Most implementations will use Carrier board
standoffs that have M2.5 threads (as opposed to clearance holes). A short
M2.5 screw and washer, inserted from the Module top side, secures the
Module to the Carrier board threaded standoff.
The SMARC connector board-to-board stack heights that are available may
result in the use of non-standard spacer lengths. The board-to-board stack
heights available include 1.5mm, 2.7mm and 5mm. Of these three, only the
spacer for the 5mm stack would likely be a standard length.
Penn Engineering and Manufacturing (PEM) (www.pemnet.com) makes
surface mount spacers with M2.5 internal threads. The product line is called