I am wondering what the purpose is of thermal reliefs? Is it to dissipate heat while the IC is operating, or to dissipate heat during the soldering processing?
Added 10 years, 2 months ago.
It is neither. Thermal reliefs prevent heat from dissipating during the soldering process.
If a pad is directly connected to a large copper area (copper pour/plane), the copper area acts to dissipate the heat due to its high thermal conductivity. The thermal relief reduces the area that is directly connected to the copper area, and so increases the thermal resistance. The increased thermal resistance makes it easier to solder.
Answered 10 years, 2 months ago.