The idea is to use one of the internal layers on a four-layer PCB, which would normally be devoted to a ground plane, as a built-in heating element.

Through soldering, different parts of the PCB are connected to other electrical components to make a PCB function properly and serve its purpose.

Tyco Electronics RYII series, RT1 series and RT2 series power PCB relays are suitable for THR (Through-Hole-Reflow) soldering processes.