Solder mask is a special ink resin based, designed to protect the PCB during the assembly step.
We use the photoimageable type, it means that we use uv light to fix the pad pattern over the pcb,
and we use it for production volume and prototype pcb too.
Photoimageable solder mask is used to produce PCB with high volume connection,
but the are some design rule that must be respected, so pay attention on the
following parameters when drawing a new solder mask.
Solder Mask CLEARANCE value : gap between copper area and solder mask edge
Solder Mask Bridge value : gap between two solder mask edges.
Industrial standard color is green,and with this color you have the best clearance value and bridge value .
Check on our pcb online calculator which color you can choose.