How to prepare your files for PCB assembly
A complete file pack gets you a faster quote, fewer questions and a cleaner first build. Here is what to send.
- Send Gerbers and drill files for every layer, plus the board outline
- List every part in the BOM with a manufacturer part number
- Include a pick-and-place file with rotation and board side
- Mark do-not-fit parts and polarity on the assembly drawing
- Say how the board should be tested
Why the file pack matters
An assembler can only build what the files describe. Missing or unclear files lead to questions, delays and guesswork, and guesswork is how first builds go wrong. A complete pack lets the assembler quote accurately, order the right parts and build the board right first time.
1. Gerber and drill files
Gerber files describe the bare board, one file per layer: each copper layer, solder mask, silkscreen and solder paste, plus the board outline. Export them in Gerber X2 or RS-274X format, together with the NC drill files. Some assemblers also accept ODB++ or IPC-2581. Add a short note or fabrication drawing with the layer stack-up, board thickness, copper weight and surface finish.
2. A bill of materials (BOM)
The BOM lists every component on the board. For each line, give the reference designators, quantity, manufacturer, manufacturer part number and a short description including the package. Mark any parts that are not to be fitted (DNP), and list approved alternatives for parts that are hard to buy. A clear BOM is the single biggest help in getting an accurate quote.
Want a second opinion on your project?
Share your files and we’ll call you within 24 hours.
3. A pick-and-place file
The pick-and-place (or centroid) file tells the assembly machines where each part goes: reference designator, X and Y position, rotation and which side of the board it sits on. State the units and the origin so the data lines up with the Gerbers.
4. An assembly drawing
The assembly drawing shows where parts sit, which way round polarised parts go (diodes, electrolytic capacitors, ICs), which parts are not fitted, and any special instructions such as hand-soldered parts, conformal coating areas or labels.
5. Test and quality requirements
Say how you want the board tested: a functional test procedure, any firmware to load, and the inspection class you need, for example IPC-A-610 Class 2 for most commercial products or Class 3 for high-reliability work. Mention any standards the finished product must meet.
Questions to ask before you send
- Is every layer and drill file included, with the board outline?
- Does every BOM line have a manufacturer part number?
- Are do-not-fit parts marked in the BOM and on the drawing?
- Does the pick-and-place file give rotation and board side?
- Is polarity clear for every polarised part?
- Have you said how the board should be tested?
- Do you need an NDA in place before you share the files?