Without Masking

copper board pelectropcb

With Masking

pcb masking pelectropcb

Advantage of Masking

1. Protecting from oxidize and rust

2. Increase  the life of PCB 

3. Protect from adherence of solder balls, solder bridging, solder build-up

4. Gives physical damage protection 

5. Protect collapse of the BGA during reflow