SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11
Design-in
Page 115 of 157
F’’
1.00 mm
J’’
0.35 mm
O’’
1.05 mm
Table 37: SARA-R4/N4 series modules suggested footprint and paste mask dimensions
☞
These are recommendations only and not specifications. The exact copper, solder and paste mask
geometries, distances, stencil thicknesses and solder paste volumes must be adapted to the specific
production processes (e.g. soldering etc.) of the customer.
2.12
Thermal guidelines
☞
The module operating temperature range is specified in the SARA-R4/N4 series Data Sheet
The most critical condition concerning module thermal performance is the uplink transmission at maximum
power (data upload in connected mode), when the baseband processor runs at full speed, radio circuits are
all active and the RF power amplifier is driven to higher output RF power. This scenario is not often
encountered in real networks (for example, see the Terminal Tx Power distribution for WCDMA, taken from
operation on a live network, described in the GSMA TS.09 Battery Life Measurement and Current
Consumption Technique
); however the application should be correctly designed to cope with it.
During transmission at maximum RF power the SARA-R4/N4 series modules generate thermal power that
may exceed 0.5 W: this is an indicative value since the exact generated power strictly depends on operating
condition such as the actual antenna return loss, the transmitting frequency band, etc. The generated
thermal power must be adequately dissipated through the thermal and mechanical design of the application.
The spreading of the Module-to-Ambient thermal resistance (R
th,M-A
) depends on the module operating
condition. The overall temperature distribution is influenced by the configuration of the active components
during the specific mode of operation and their different thermal resistance toward the case interface.
☞
The Module-to-Ambient thermal resistance value and the relative increase of module temperature will
differ according to the specific mechanical deployments of the module, e.g. application PCB with
different dimensions and characteristics, mechanical shells enclosure, or forced air flow.
The increase of the thermal dissipation, i.e. the reduction of the Module-to-Ambient thermal resistance, will
decrease the temperature of the modules’ internal circuitry for a given operating ambient temperature. This
improves the device long-term reliability in particular for applications operating at high ambient
temperature.
Recommended hardware techniques to be used to improve heat dissipation in the application:
Connect each
GND
pin with solid ground layer of the application PCB and connect each ground area
of the multilayer application PCB with complete thermal via stacked down to main ground layer.
Provide a ground plane as wide as possible on the application board.
