Files and drawings
- Gerber (RS-274X) — the image data for each layer: copper, mask, legend, outline.
- Excellon drill file — hole coordinates and finished diameters, with plated and non-plated holes separated.
- Fabrication drawing — the document that states stack-up, materials, copper weights, finish, tolerances, acceptance class and any special process.
- Netlist — the logical connection list used to verify that the board matches the schematic during electrical test.
- Test coupon — a test structure on the panel used for cross-sections and impedance measurement.
Stack-up and materials
- Core — a fully cured laminate (C-stage) with copper on both faces. It gives the board its mechanical stability.
- Prepreg — glass fabric pre-impregnated with partially cured resin (B-stage). It flows under heat and pressure, bonds the cores and becomes the dielectric between them.
- Copper weight — foil weight per square foot; 1 oz ≈ 35 µm.
- Tg — glass transition temperature of the laminate; above it the material expands faster and dimensional stability drops.
- CTE — coefficient of thermal expansion, usually quoted in ppm/K and dominated by the Z axis on a laminate.
Features
- Trace and space — conductor width and the gap to its neighbour; 0.075 mm is the plant minimum on fine-feature layers.
- Via — a plated hole connecting layers. Through, blind (reaches one outer layer) and buried (stays inside) are the basic types; a microvia is laser-drilled at 0.1 mm and connects adjacent layers.
- Annular ring — the copper ring around a drilled hole; how much remains after drill tolerance decides whether the connection survives.
- Aspect ratio — board thickness divided by hole diameter, 15:1 here; deeper holes cannot be plated evenly.
- PTH / NPTH — plated through hole versus non-plated hole (mounting, alignment).
- Solder mask — the polymer layer that keeps solder off everything except the pads; legend is the printed marking, often called silkscreen.
- V-score — a V-shaped groove for separating boards; it leaves a visible line on the edge. Routing cuts the outline with a bit instead.
Finishes
- HASL — hot air solder levelling; cheap, uneven surface, best for coarse pitch.
- ENIG — electroless nickel immersion gold; flat, good for fine pitch, costs more.
- OSP — organic solderability preservative; cheapest and flattest, shortest shelf life.
- Immersion silver / tin — flat alternatives with their own storage rules.
Panel, test and assembly
- Array / panelisation — arranging boards on a panel with tooling strips and coupons.
- Fiducial — a copper or mask-free mark the placement machine uses to align.
- Impedance coupon — a test structure measured to prove the stack-up hit its target.
- DFM / DFA / DFT — design for manufacturing, assembly and test: the three reviews before tooling.
- PCBA — a bare board with components assembled, soldered and tested.
The limits behind these terms are on the capability page; the fabrication process itself is described step by step in the manufacturing process note, and the assembly side on the PCBA manufacturing page.
