firstly it capacitor, and what you need to do is buy good iron that you'll use forever like maybe an 80watt soldering iron (station)
so that you can have the parts hot enough to have the solder adhere to it.
plus which motor are you trying to solder capacitiors on:
if it is the fantom epic motor like mine forget it, those three little things soldered on the green board is the three capacitors. if you are trying to solder the capacitors to a 540 johnson also forget it as they are alredy installed inside the can.
see ya
hey any of ya friends want to buy ma motors.