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90 DESIGN007 MAGAZINE I APRIL 2022 Article by Anaya Vardya AMERICAN STANDARD CIRCUITS Introduction One of the biggest challenges facing PCB designers is understanding the cost drivers in the PCB manufacturing process. is article is the latest in a series that will discuss these cost drivers from the PCB manufacturer's perspec- tive, and the design decisions that will impact product reliability. Solder Mask Availability Most shops provide a variety of solder masks to satisfy the needs of all customers. Table 1 is a description of typical solder masks cur- rently available. e need for closer tolerances has driven the implementation of laser direct imaging (LDI) solder masks (laser-defined solder mask pattern instead of screening). Solder mask is a protective coating that shields selected areas of a PCB from oxidation, handling and unwanted solder during assem- bly. • Solder mask allows a 0.003" web to be placed between pads in an SMD array, provided the minimum spacing between these pads is 0.007" (by design). • Green solder mask allows a 0.003" web to be placed between pads in an SMD array, provided the minimum spacing between these pads is 0.007" (by design). All colors cannot maintain this dam size. DFM 101: Solder Mask and Legend Table 1: Description of typical solder masks available. Figure 1: Green is the preferred solder mask color.