There is nothing more frustrating than ordering a batch of custom circuit boards only to discover a missing drill file, inverted silkscreen polarity markings, or an unintended short-circuit beneath a fine-pitch IC. Running a systematic pre-flight engineering checklist before exporting your RS-274X Gerber files saves weeks of project delays and prevents costly scrap. Here is the exact checklist our engineering team at Tamizh Tech uses before releasing designs for fabrication.
1. Schematic and Netlist Synchronization
- Check ERC (Electrical Rules Check): Verify zero unconnected input pins, duplicate net names, or conflicting power flags.
- Forward-Annotate Netlist: Ensure the layout board editor is 100% synchronized with the latest schematic revision.
- Inspect Decoupling Capacitors: Verify that 0.1µF ceramic bypass capacitors are placed physically adjacent to every microcontroller VDD pin rather than grouped in a far corner.
2. Physical Design Rule Checks (DRC)
Configure your EDA tool's DRC constraints to match real fabrication capabilities. For standard prototype boards: (1) Minimum trace width ≥ 6 mil (0.15mm), (2) Minimum trace clearance ≥ 6 mil (0.15mm), (3) Minimum drill hole diameter ≥ 0.3mm, and (4) Minimum annular ring width ≥ 0.15mm around plated vias.
3. Thermal Reliefs and Solid Copper Pours
Ensure all through-hole pins and SMD component pads connected to large ground or power copper planes use thermal relief spokes (typically 4 spokes at 45° or 90°). Connecting pads directly to massive solid copper pours draws heat away during soldering, resulting in cold solder joints or tombstoning during reflow.
4. Silkscreen Legend and Polarity Indicators
| Component Type | Polarity Verification Rule | Common Failure Mode |
|---|---|---|
| Diodes & LEDs | Cathode clearly identified with line or bar | LEDs soldered in reverse, failing to illuminate |
| Electrolytic Capacitors | Positive (+) or negative (-) terminal marked | Capacitor rupture from reverse DC bias |
| Integrated Circuits (ICs) | Pin 1 dot or notch visible beyond IC body | IC rotated 180°, shorting power to ground |
| Connectors & Headers | Pin 1, VCC, GND, and signal labels visible | Cables plugged in backwards during field bring-up |
5. Gerber File Pre-Flight Inspection in a Standalone Viewer
Never send Gerber ZIP files directly from your EDA export folder without first loading them into an independent Gerber viewer (such as Gerbv or KiCad Gerber Viewer). Toggle layers individually to verify: (1) drill holes align with copper pad centers, (2) board outline is present on a dedicated mechanical layer, and (3) no silkscreen text overlaps exposed solder pads.
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