Often, thermal conductivity is one of the first and primary parameters used when selecting a TIM. However, often what is far more important is choosing a TIM that can both minimize contact resistance (voids) and BLT. Thinking about it, even a TIM with relatively poor conductivity could provide superior performance if coverage and thickness is far better than a higher conductivity material. For this reason, Xilinx suggests focusing on the characteristics and application of TIM that ensures best coverage, contact, and BLT first, and the overall conductivity as a secondary parameter for TIM choice. Also, while the TIM material has to be thermally conductive, it should not be electrically conductive to minimize the chances of electrical shorts both inside and outside packages. Finally, long term stability and reliability should also be an obvious consideration with TIM choice.