Solder mask or solder resist is a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads. 

90% of solder mask is in Green color, balance can be found in White, Black, Blue, Red, Yellow and more. Green color is easy to be made, Black is the most difficult one, other colors are moderate.

Solder mask bridge, means the solder mask between the pads of IC. It exists to prevent the flowing of tin to avoid short circuits. What’s the width of solder mask bridge? It depends on the capability of factories.

At Heneng Technology, our capability is as follows:

  • For Green solder mask, the width of solder mask bridge is 3 mil. So the gap between pads is 7 mil.
  • For Black solder mask, the width of solder mask bridge is 4 mil, So the gap between pads is 8 mil.
  • For other color solder masks, the width of solder mask bridge is 3.5 mil, and the gap between pads is 7.5 mil.

Sometimes, PCB designers don’t know this, so in their design, the pads gap is 7 mil but they request Blue or Black color solder mask. Our engineering team will have to send them an EQ (Engineering Query) with two options for them to choose:

  • Don’t make the solder mask bridge, leave them as full opening and accepting the risk of short circuits.
  • Shave the pads to make enough space for solder mask bridge.

Feel free to leave any comments to discuss with our engineering team.