What are the layers of a PCB, and what are they made of?

A printed circuit board (PCB) consists of several distinct layers, each serving a specific purpose. Here are the primary layers of a PCB and their materials:

  1. Substrate/Core Layer:
    • Material: Typically made of fiberglass (FR4) or other insulating material.
    • Purpose: Provides mechanical support and the base structure of the PCB.
  2. Copper Layer:
    • Material: Copper foil.
    • Purpose: Forms the conductive pathways (traces) that connect different components.
  3. Solder Mask Layer:
    • Material: Liquid photo-imageable (LPI) solder mask or epoxy-based resin.
    • Purpose: Insulates the copper traces to prevent short circuits and protect against environmental damage.
  4. Silkscreen Layer:
    • Material: Ink (usually white, but can be other colors).
    • Purpose: Provides labeling and identification marks for components and test points.
  5. Dielectric/Prepreg Layer:
    • Material: Epoxy resin (often FR4) impregnated fiberglass.
  • Purpose: Insulates different copper layers from each other and bonds them together during the lamination process.
  1. Copper Planes (Power/Ground Planes):
  • Material: Copper foil.
    • Purpose: Provides a stable voltage reference and helps in power distribution and signal integrity.
  1. Surface Finish Layer:
    • Material: Various options like HASL (Hot Air Solder Leveling), ENIG (Electroless Nickel Immersion Gold), or OSP (Organic Solderability Preservatives).
    • Purpose: Protects the exposed copper and provides a solderable surface for component attachment.