much of the layout work. Multilayer PCBs allow for much higher component density because the component paths on the inner layers would occupy the space between the components. The increase in the need for multilayer printed soldermask circuit boards with more than two, four and especially more than six layers of copper has been concurrent with
usually unwanted, circuit elements; rather, they can be used as part of the soldermask circuit design, as in distributed element filters, antennas, and fuses, avoiding the need for additional separate components. High Density Interconnect (HDI) PCBs have traces and/or insulation less than 125 micrometers in width or diameter.
usually printed with a non-conductive permanent epoxy ink. The color is usually white, although other colors are available: yellow, black, blue, red. Screen printing is used to render useful information on the PCB board that can help users during assembly. It is used to mark component values, soldermask part numbers, test points, polarity, etc. Screen