Having good thermal performances could have various meanings depending on the end equipment (EE).

Some systems, like Industrial PCs, have a specified board temperature you cannot exceed. In this case, the board designer has to ensure that the heat dissipation of the IC is optimized through a good layout and cooling system. In other end equipment, like security cameras, a defined operating ambient temperature is required and the designer needs to ensure that the IC stays within the specified recommended operating junction temperature for reliable operation. In other systems, like Solid State Drive (SSD) Memories, the board heats up mainly from other ICs, like the SSD controller. In such cases, the heat dissipation through the board is limited due to its restricted size and form factor. The system designer needs to make sure the power IC package is able to support a good board to top heat dissipation to stay within the recommended junction temperature and avoid unwanted behavior like thermal shutdown.