Soldering bullet connectors to the ESC (Electronic Speed Controllers) that will later go between PCB (Power Distribution Board) and Brushless Motors that lift he quadcopter off the ground.

Soldering pins to the PCB.

I use the Rosin-core solder which helps to deoxidize the connection and makes the bond stronger. However the residue of the flux has to be wiped of with pure alcohol immediately after use or it might be later harmful to the PCB.

Two 14 gauge flexible silicone cables will connect with a high-discharge LiPo battery.