— A backing plate may be necessary on the back side of the printed circuit board (opposite to the flip-chip device) to
prevent board warpage.
• Consider the temperature limits beneath the heatsink and ensure that the temperature-sensitive components are not
placed there to prevent overheating and damage.
• Ensure that the orientation and spacing of the fins causes the heat to move as quickly as possible from the heat source
(see Air Flow Considerations).
— Improper orientation can inhibit the thermal performance of the heatsink.
See
Assembly Handling and Thermal Solutions for Lidless Flip Chip Ball Grid Array Packages
(document AN4871) for more
heatsink handling details.
4.10 Thermal simulations
As illustrated in this section, thermal management is a very complex discipline with numerous variables that must be considered.
To determine whether the system is capable of stable operation (no thermal runaways) in the given use case or to identify
potentially overlooked issues, thermal simulations must be performed.
NXP can provide FloTHERM simulation models for the i.MX 8 series processor family and strongly encourages customers to
perform thermal simulations using these models in their form factor designs and specific use cases to get a holistic system thermal
design and identify possible thermal bottlenecks. Thermal simulations become increasingly important in small form factor designs
and in operation in high ambient temperatures.
4.11 Software optimization
Software-based power and thermal management techniques can be very effective in reducing the need for more elaborate active
or passive thermal management solutions and add little or no additional cost to the system design. Attention should be paid to the
required system performance and power requirements, because lowering the i.MX 8 processor power consumption also lowers
the heat generated by the processor.
The i.MX 8 series incorporates several low-power design techniques to meet requirements of low-power design, while sustaining
high performance. The activity profile of the customer application can have a significant impact on the thermal management
techniques used and on the TDP. Carefully defining the system’s worst case operating conditions can be an effective way to
reduce power and thermal dissipation.
• System designers should utilize and enable all software power-management techniques available for the i.MX 8 series.
• The SoC voltages and core frequencies of modules should be kept at the minimum specified levels and scaled
dynamically with respect to the current performance demands of the application, where possible.
• The processor should enter low-power modes under certain use cases whenever possible.
• All unused power rails should be turned off from the PMIC and unused domains should be power-gated, if possible.
• All unused module clocks should be turned off (dynamically handled by the NXP Linux BSP).
• Customers are encouraged to use the latest Linux BSP GA release available on nxp.com that leverages the i.MX 8
processor power-management features and incorporates various Linux OS software power-management techniques.
4.12 Thermal checklist
NXP recommends using the checklist shown in Table 39 as a high-level guide for designing an optimal thermal management
solution for your end product.
NXP Semiconductors
Thermal considerations
i.MX8 QM / i.MX8 QXP Hardware Developer’s Guide, Rev. 2.4p, 06/2021
User's Guide 79 / 89
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