Basic PCB Construction

Circuit board and flex materials are selected around electrical and environmental properties required to operate based on the schematic. The schematic dictates the number of layers and the form factor of the board. Typically, a board supplier will provide a stackup of the selected materials based on your design. This could be a number of layers — not just 4.

Substrate: This refers to the supporting material used in a PCB that holds the components and traces.

Copper: This highly conductive element is used to make the signal traces that conduct electricity.

Solder mask: This is a technique in which all parts of a circuit board are coated with epoxy except the contacts to be soldered, the gold-plated terminals of any card-edge connectors, and fiducial marks.

Silkscreen: The ink is digitally printed and doesn’t impact the function of a PCB, but it’s an equally important part of a PCB’s construction. Also known as a “silkscreen legend,” this refers to the decals and reference designators in epoxy ink printed on a PCB. A silkscreen will help you recognize warning symbols and identify components and where they are to be placed. A silkscreen will also identify test points and manufacturer marks and more. The ink is typically white, and black may also be used at times when the substrate is white in color.

Here are some technical terms you may come across when it comes to PCB construction:

  • Annular ring — The copper ring surrounding the holes on a printed circuit board
  • Design rule check — A prescribed process of double-checking a PCB for manufacturability
  • Blind and buried vias — A method of layer to layer connections in a printed wiring board that is used to route a trace vertically in the board from one layer to another without a plated through hole
  • Trace — Trace is the copper structure that the signals go through; it is commonly referred to as a wire, although it isn’t. It’s the same purpose as a stand alone wire except it is laminated to the substrate and formed by imagine process and etching process.
  • Surface mount — Where components are placed by SMT automated equipment and  soldered to the board in a conveyorized reflow oven
  • Plated-through hole — A drilled hole in the PCB with copper plating added after it is drilled