Ordering assembled boards (PCBA) for the first time can feel like a wall of file formats. In practice you need three files and a few decisions. Get them right, and quotes come back fast and boards come back working.
New to this? Start with What is PCBA?
File 1: Gerber files (the board)
Gerber files describe your bare board: each copper layer, the solder mask, the silkscreen text, and the board outline. Drill files (the holes) come with them. Your PCB design software (KiCad, Altium, EasyEDA and others) exports them, usually as a ZIP.
Check before sending: open them in a free Gerber viewer and make sure every layer is there and the outline is closed.
File 2: the BOM (the parts list)
The BOM (bill of materials) lists every component. For assembly it must include:
| Column | Example |
|---|---|
| Designator (where it goes on the board) | R1, R2, C5, U1 |
| Quantity per board | 2 |
| Manufacturer part number (MPN) | GRM155R71C104KA88D |
| Description | 100 nF 16 V 0402 capacitor |
| Package / footprint | 0402 |
| Approved alternatives (optional) | … |
The most common problem is a BOM with vague descriptions ("10k resistor") instead of exact part numbers. It causes wrong parts and delays. Mark any parts the factory should not fit ("DNP", do not place).
File 3: pick-and-place (centroid / CPL)
This file tells the machine the exact position and rotation of each component. Your design software exports it (as "pick and place", "centroid" or "CPL", depending on the tool). Make sure the designators match the BOM.
Decisions the factory will ask about
- Quantity: how many boards (and whether to quote a few quantities).
- Board specs: layers, thickness (1.6 mm is standard), copper weight, solder mask colour, surface finish (HASL or ENIG. ENIG is flatter and better for fine-pitch chips).
- Parts sourcing: turnkey or consigned?
- Panelization: small boards are often joined into a panel for the machines. The factory can do this.
- Testing: AOI is usually standard. Do you need X-ray (for BGA chips), a functional test, or programming firmware onto the chip?
- Conformal coating or special cleaning? Only if your product needs it.
Tips for a smooth first order
- Order a few extra boards. Prototypes break, and the extra cost is small.
- Ask for a DFM check before production. Most shops run your files through one and flag problems.
- Confirm component substitutions in writing. If a part is out of stock, the factory will propose alternatives. Check them against your design.
- Add test points to your design so boards can be tested quickly.
Next steps
- How much does PCB assembly cost?
- Upload files to online platforms or request quotes from PCBA shops
Updated 29 September 2026
