Files Needed for a PCB Assembly Quote: Gerber, BOM and Pick-and-Place

By PCBIOT engineering team · 14 October 2026

Getting a fast and accurate PCB assembly (PCBA) quote depends mostly on the files you send. Incomplete data leads to back-and-forth emails and delays. Here is what an assembler normally needs and how to prepare it.

1. Gerber files for the bare board

Gerber files (usually RS-274X format) describe each layer of the board: copper layers, solder mask, silkscreen and the board outline. Include the drill files (commonly Excellon format) so the holes and vias are defined. Zip them into one folder and name the revision clearly.

2. Bill of materials (BOM)

The BOM lists every component to be placed. A good BOM has these columns:

• Reference designators (for example R1, R2, C5, U1)
• Quantity per board
• Manufacturer and manufacturer part number (MPN)
• Description and package or footprint
• Notes such as “do not populate” (DNP) or approved alternates

Manufacturer part numbers matter more than descriptions. A line that only says “10k resistor” forces the assembler to guess tolerance, power rating and package.

3. Pick-and-place (centroid) file

This file gives the position of each component for the placement machine: reference designator, X and Y coordinates, rotation and which side of the board the part is on. Most PCB design tools can export it. Check that the reference designators match the BOM exactly.

4. Assembly drawing and special instructions

Mark anything that is not obvious from the data: which parts are through-hole, parts to fit by hand, polarity of connectors, glue or conformal coating requirements and where to keep clear areas.

5. Quantity, timeline and testing

State how many boards you need now and expected future volumes, your target delivery date and any test requirements. If you have a functional test procedure or programming file, mention it early.

Common mistakes that cause delays

• Reference designators that differ between the BOM and the pick-and-place file.
• BOM lines without manufacturer part numbers.
• Obsolete or out-of-stock parts that are only discovered at ordering time.
• Footprints that do not match the datasheet.
• Missing drill file or board outline in the Gerber package.

Related reading

Review your design with our DFM checklist, learn the difference between SMT and THT, or go straight to our PCB assembly service. If parts are hard to find, our supply chain team can help with sourcing.