User`s guide

Chapter 3 - Receiver Descriptions
PCB Mounting Hardware
The M12+ Oncore PCB is normally mounted on round or hex female threaded metal standoffs
and retained with metal English or metric screws. Mounting standoffs are available in a wide
variety of materials with English or metric threads. Several sources are listed in Table 3.5. Key
points in selecting the four screws and standoffs that will mechanically hold and secure the M12+
to the application PCB are the screw sizes, screw head designs, and the diameter and length of
the standoffs.
The four holes in the M12+ PCB are designed to accommodate 4-40 (English) or 2.5 or 3mm
(metric) mounting screws. It is recommended that these screws have Philips, Torx, or other head
designs that retain the installation tool in order to avoid component damage that may occur if the
tool slips out of the screw head. Recommended torque to assemble the M12+ PCB to the
standoffs is 6 in-lb, with a maximum of 7 and minimum of 5 in-lb. While somewhat higher torques
can be tolerated, use of extremely high torques can possibly crack internal clads in the four-layer
M12+ PCB. Washers are not required or recommended.
Standoffs should have a maximum outside diameter (OD) of .187" (4.5mm). Note that these are
standard sizes and should be easy to procure from a number of sources. Use of larger diameter
standoffs can result in damage to small surface mount components mounted in close proximity to
the mounting holes. If standoffs of the recommended diameters are not available, the next larger
available diameter may possibly be used, but fit should be carefully verified before committing to
large-scale production.
Obviously the height of the standoffs will be determined by the components that are populated on
the application PCB, especially the height of the 10-pin receptacle. See Figures 3.4 and 3.5,
which are outline drawings of the M12+ receiver. The drawings describe the overall placement
and height of large components and connectors populated on both sides of the M12+ PCB.
Motorola GPS Products - M12+ User's Guide Revision 6.X 09FEB05
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