PCB solder mask is used to provide a hard, durable solder resistant coatings with electrical insulation. Solder masks can be used to protect vias from process solutions and soldering. The electrical insulation properties of solder mask depend on the thickness applied and the type of mask used.
All PCB markings and/or legends required for the end user must be specified on the master drawing. The marking type (non-conductive ink, etched characters, or other methods) must be clearly specified. Markings should be placed to avoid being covered by components and should not be on the conductive surface. As long as practical, part number, revision, layer number and orientation markings should be included on the master drawing. Most non-conductive inks are liquid screened, markings within 0.020" MAY be slipped 0.005" or more from solderable surface. Note that the readability of liquid screened markings is affected by high surface irregularities.
All materials that are part of the finished product are certified to meet the master drawing and/or purchase documents. You must outline the conformance assessment required by the end user on the master drawing. The master drawing must contain a coupon configuration for conformance assessment. Where feasible, coupons are located in the center of each panel to best reflect plating characteristics. All coupons (whether for conformance or process control assessments) are determined by board number, version, lot number, logo and date code.