Thermal Resistance of the SOT-223 Package

[Matsuura]

I am selecting the LD1117S50CTR. The package is SOT-223.
I understand that the thermal resistance Rthja = 110 °C/W shown in the datasheet is the value for the IC alone.
Since I am designing the PCB, I would like to know the relationship between copper area and thermal resistance.
I would appreciate your advice.

[RobK1]

This Application Note from TI might be helpful:

https://www.ti.com/lit/an/snva036b/snva036b.pdf

[Matsuura]

I truly appreciate your support.

[Matsuura]

I appreciate your thoughtfulness.