The permissible power dissipation of an unmounted IC is rated without any heat sink or any heat dissipation path through a printed circuit board. Without heat dissipation, an application of a large electric current causes an IC to heat up, leading to thermal shutdown (TSD) of the IC. If the IC is left in this condition, its temperature exceeds the absolute maximum temperature, increasing the likelihood that it will be permanently damaged.
Therefore, consult application notes for each device and create a thermal design that allows sufficient temperature margin so that the junction temperature will not exceed 150°C. In addition, keep in mind that an increase in ambient temperature reduces the permissible power dissipation.