What is solder mask dam?
Solder mask bridge, also known as green oil bridge, solder mask dam, is the green oil between the spacing of the SMD pads to SMD pads (the width of the solder resist ink between the two soldermask openings).
Solder Mask Dam
Solder mask is very important when it comes to batch PCB assembly. Printing solder mask between the pads requires solder mask dam between pads. Generally the minimum solder mask min dam size is 4mils. If the clearance between pads is less than 4mil, it is difficult to print the solder mask. The minimum solder mask dam is the minimum width of the solder resist between the pads to pads.
Soldermask dam is an "isolation zone", in order to prevent short circuit of the SMD components. If it is possible, always set solder mask dams between the surface mount device pads, especially critical for fine pitch IC. This helps prevent accidental solder bridging during assembly and greatly reduces the amount of rework. If there is not enough space between pads, the soldermask dams have to be removed.
