I’ve been looking for something like this for a while. Enjoy.
This Instructable is about dry film solder mask, in other words, is the green stuff that is on top of the circuit board.
I like to use smd components in my circuits board because I don’t have a computerized drill machine and do in it by hand for a big
boards are really tedious.
Soldering smd components in a copper board without dry solder mask, especially for those little capacitors and resistor of 402 in size, becomes a tough challenge and of course those micro controllers with almost zero space between pins.
Read more here