Thermal Interface Material - Thermal Interface Material - AM013

When installing heat sinks for Versal devices, a suitable thermal interface material (TIM) must be used. This thermal material significantly aids the transfer of heat from the component to the heat sink.

For lidless and bare-die flip-chip BGAs, the surface of the silicon contacts the heat sink. For lidded flip-chip BGAs, the lid contacts the heat sink. The surface size of the lidless or bare-die flip-chip BGA and lidded flip-chip BGAs are different. AMD recommends a different type of thermal material for long-term use with each type of flip-chip BGAs package.

Thermal interface material is necessary because even a large heat sink and fan cannot effectively cool an Versal device without good physical contact. The base of the heat sink and the top of the Versal device must have proper contact. The surfaces of the heat sink and the Versal device silicon are not perfectly smooth.

You can observe this roughness at the microscopic level. Surface roughness reduces the effective contact area. A heat sink without thermal interface material cannot provide sufficient surface contact.

Thermal interface material fill gaps and transfer heat between the Versal device die and the heat sink. Use phase-change material, thermal grease, or thermal pads.

The selection of the thermal interface material (TIM) between the package and the thermal management solution is critical to ensure the lowest thermal contact resistance. Therefore, the following parameters must be considered.

1. The flatness of the lid and the flatness of the contact surface of the thermal solution.
2. The applied pressure of the thermal solution on the package must be within the allowable maximum pressure for the package. Use a smart-torque tool when applying a thermal solution to control the rate of short-term transient pressure as the TIM relaxes. Also follow the TIM supplier's specifications.
3. The total thermal contact of the thermal interface material. This value is determined based on the parameters in step 1 and step 2, which are published in the data sheet of the TIM supplier.