... Board Thickness/Hole Ratio: 12:1 Min. Solder Mask Bridge: 4mil (Min. SMT Pad Space 8mil) ... 30mil Min. drilling slot size: 0.6mm Solder mask color: green, black, blue, white, yellow, ... and matt, etc. Solder mask hardness: 6H Legend/Silkscreen Color: white, yellow, ... , etc. Other Technology: Gold finger, peelable mask, Non-across blind/buried vias, characteristic impedance control ...