under Maximum ratings (page 7) package you can see that Thermal resistance junction-case is always smaller then Thermal resistance junction-ambient
i can't see why, if i understand this correctly this data tells me how many degrees (in celsius) is emitted to the ambiant and/or the case for 1W of dissipated power.
the reasonable thing to belive is that inside the case its much hotter then the ambiant.
The thermal resistance of junction-to-ambient equals the junction-to-case resistance plus the case-to-ambient.
Thermal resistance is the difference in temperature between one part and the other when a watt of power is being conveyed from one to the other.
It is an analog to ohmic resistance which is the electric potential difference between two points when one Amp of current is passing from one to the other.