Heat Sink Guidelines; Bolt-Down Style; Adhesive Style Heat Sink - Digi XB3-C-A2-UT series User Manual

Design recommendations

Heat sink guidelines

Based on the results of your thermal testing you may find it is advisable or required to implement a
method of dissipating excess heat. This section explains how to employ a heat sink on top of the XBee
Smart Modem.

Bolt-down style

A bolt-down style heat sink on top of the XBee Smart Modem provides the best performance. An
example part number is Advanced Thermal Solutions ATS-PCBT1084/ATS-PCB1084. You must use an
electrically non-conductive thermal gasket on top of the XBee device under the area that will be
covered by the heat sink. A thermal gasket such as Gap Pad® 2500S20 is suitable for this purpose. We
recommend using a gasket with thickness of 0.080 in to ensure that components on top of the XBee
device do not tear through the material when pressure is applied to the heat sink.
Install the SIM card prior to placement of the heat sink. Position the thermal gasket and heat sink
assembly on the top of the device so that it covers the microcontroller and surrounding components.
You may cover the section shown inside the red box below; do not cover the U.FL connectors. When
attaching to the host PCB, tighten the mounting hardware until the thermal gasket is compressed
about 25%. Avoid overtightening. To prevent shorting, check that the surface of the heat sink does not
directly contact the XBee device.

Adhesive style heat sink

For applications where the size or mounting requirement of the bolt-down heat sink is undesirable,
you may alternatively employ an adhesive style heat sink. The heat sink should be no more than 8x8
mm in size (one option is the Assman WSW Components V2016B). Use a thermally conductive epoxy to
Digi XBee3 Cellular LTE-M Global Smart Modem User Guide
Heat sink guidelines
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