When designing your system to mate with the K26 SOM, the design must consider the following items.
- Thermal Solution
- A system thermal solution is capable of cooling the appropriate amount of TMP for the target workload.
- Thermal Interface Material (TIM)
- The TIM is the thermally conductive compound between the heat sink and the device. This material fills the air gaps and voids and enhances the transfer of heat from the device to the heat sink. Your design must include the TIM between the K26 SOM heat spreader and your system thermal solution. For the best thermal performance, the TIM should provide the lowest thermal impedance within the mechanical, reliability, and cost constraints of the end product.
- Maximum Temperature
- The thermal solution design must ensure that the maximum Zynq UltraScale+ MPSoC based K26 SOM operating temperature is less than the value specified in Table 1 and that the maximum component temperatures on the PCB do not exceed the values specified in Table 1.
The following illustration is of a thermal stack-up.
Figure 1. K26 SOM Thermal Stack-up
The overall system thermal solution is the mechanical element that interfaces to the K26 SOM and provides cooling. A variety of thermal solution configurations (passive cooling, air cooling, and liquid cooling) are possible, depending on the system design. In all cases, the following recommendations are applicable:
- Good contact between the thermal solution and the K26 SOM is critical for maximizing performance. In general, the K26 SOM consumes the majority of the TMP.
- You must ensure that the system thermal solution has the appropriate
direct-contact surface mounting on the heat spreader top to cover all selected
heat sources.Recommended: The recommended contact pressure is between 20 and 30 PSI.
- The cooling solution must be capable of maintaining the surface temperature on top of the heat spreader at or less than the values specified in Table 1.
- The four M3 mounting holes on the heat spreader are provided to accommodate
a variety of thermal solution assembly variances in your system design. Spring
screws are recommended to maintain the contact pressure within a specific range
with a preset torque driver.Recommended: Ensure the bond-line thickness (BLT) is kept to a minimum to ensure an optimal thermal solution, where the recommendation is below 0.5 mm. A TIM with a thermal conductivity of ~5.0 W/mK is also recommended.
The following figure shows the recommended thermocouple locations on the top heat spreader to verify cooling performance (dimensions in mm). The four M3 holes are reserved for the cooling installation in your system design.
Figure 2. Recommended Contact Area and 7X Thermocouple Locations on Top Heat Spreader for Characterization and Debug