Solder mask comes in several media relying upon the stress of the applying. The lowest-cost solder mask is epoxy liquid that's silkscreened through the pattern onto the PCB. different sorts square measure the liquid photomageable solder mask (LPSM or LPI) inks and dry-film photoimageable solder mask (DFSM). LPSM are often silkscreened or sprayed on the PCB, exposed to the pattern and developed to supply openings within the pattern for components to be soldered to the copper pads. DFSM is vacuum-laminated on the PCB then exposed and developed. All 3 processes usually undergo a thermal cure of some sort once the pattern is outlined though LPI solder masks also are out there in radical violet (UV) cure.
Most significantly, the solder mask keeps the solder on the pads, as opposition flowing onto traces, planes, or empty board area. This reduces the chance that solder can type bridges (unintended connections) from one component to a different. Solder masks square measure vital for wave fastening, that could be a production technique. But, solder masks additionally create hand fastening quicker, easier, and a lot of correct.
A lack of solder mask isn’t the maximum amount of a problem, nevertheless a solder mask will cut back fastening time by guiding solder to the pads. (In any case, I haven’t encounter a manufacturer that provides silkscreen while not solder mask.)
If your PCB style is straightforward, you may DIY your own solder mask templet with a sharpie. Overlay a bit of transparency glaze over the PCB and mark within the pads and vias employing a fine tipped sharpie. you will need to double informed transparency film to form the pads a lot of darker, which is able to be useful to dam out the ultraviolet radiation|ultraviolet illumination|UV|actinic radiation|actinic ray} light once exposing the solder mask rosin.