The most common package used in Xilinx devices for over 10 years is lidded flip chip packages. Lidded flip chip packages offer very good power and signal integrity, and improved junction to board and junction-to-case thermal resistance as compared to wire bond packages. The lids are generally constructed from a nickel plated copper material. Xilinx uses a TIM1 material, which is thermal interface material applied by Xilinx within the lidded device package to thermally couple the die to the device lid. This material ensures good coverage as well as good thermal conductivity to further improve the junction to case thermal performances. However, the TIM 1 applied offers optimal thermal performance across the wide range of applications and industries. It must also be able to withstand the high temperatures of solder re-flow. This means while it is optimal, it might not perfectly meet a customers requirements for High power or High ambient applications. Lidless packages allow users to select the TIM based on their requirements and it is also applied after the soler re-flow process. There are two types of lids used in Xilinx lidded flip chips, and it is good to become familiar with this for mechanical fit and to evaluate thermal properties.