PCB and electronics assembly: design rules
Making and populating circuit boards, usually with surface-mount parts placed by machine.
Typical tolerance
Standard fabrication: trace and space about 0.1 mm (4 mil), via drill about 0.3 mm; finer is possible at higher cost.
Files to send
Gerber (RS-274X) plus drill file, a BOM with manufacturer part numbers, a pick-and-place (centroid) file and an assembly drawing.
Common materials
FR-4 (standard), aluminium-core for LEDs, flex and rigid-flex for special cases.
The rules, with reasons
- Standard capability first. Stay within the fab house's standard trace, space and via sizes unless you must go finer. Why: Advanced capability costs more and lowers yield.
- BOM. Give manufacturer part numbers and approved alternates; prefer common parts and footprints. Why: Unavailable parts delay or stop the build.
- Fiducials. Add at least three fiducial marks per board (and per panel). Why: Placement machines align to them.
- Panelisation. Use tabs or V-score and keep parts away from board edges. Why: Parts near edges are damaged when boards are depanelled.
- Radio modules. Use a module that already carries FCC approval for its radio. Why: It lets you skip a large share of compliance testing.
Before you ask for a quote
- Gerber, drill, BOM, centroid files
- Quantity and panel size
- Assembly side (one or both)
- Testing needs
- Compliance (FCC, CE, UL) for the finished product
Common mistakes
- BOM without part numbers
- Parts out of stock
- No fiducials
- Components too close to the board edge
Agents and scripts can check a design automatically with the check_design MCP tool or POST /api/design-rules. How to connect.
Request a quote Find manufacturers
Typical rules of thumb, not a guarantee. The manufacturer's own design guidelines override them: ask for them and check your design against both before ordering.