- Send one complete package, all at the same revision. Files arriving in pieces cause most avoidable NPI delays.
- Send ODB++ or IPC-2581 if your manufacturer accepts it, plus Gerbers and drill files as a universal fallback.
- Include a centroid (pick-and-place) file with reference designator, X-Y, rotation and side for every placed part, and double-check rotation on polarized parts.
- Send the BOM as an Excel file with a manufacturer and part number on every line, and list approved alternates for parts that go out of stock.
- State your requirements in writing: IPC class and revision, test and inspection needs, solder alloy, and any special processes.
The checklist
Board data
- ODB++ or IPC-2581 if your manufacturer accepts it. These intelligent formats carry more data with less room for interpretation.
- Gerber files: one per copper layer, plus top and bottom solder mask, silkscreen and solder paste.
- NC drill file(s) for vias and through-hole component holes.
- Fabrication drawing: stack-up, materials, finish, thickness, impedance requirements and the bare-board class (needed whenever your manufacturer sources the bare boards).
Assembly data
- Bill of materials (BOM) as an Excel file, not a PDF, with manufacturer and part number on every line (see below).
- Centroid / pick-and-place file covering every machine-placed part.
- Assembly drawing (PDF): your workmanship standard (for example, IPC-A-610 and the class), polarity and pin-1 marks, reference designators the silkscreen can't fit, do-not-populate (DNP) locations, hand-solder or keep-out areas, conformal-coating areas, and hardware.
Requirements
- IPC class and revision, for example "IPC-A-610, Revision J, Class 2". See our Class 2 vs. Class 3 guide.
- Inspection and test requirements: X-ray on BGAs, electrical test, and functional test procedures and fixtures, if you're supplying them. See our inspection and test guide.
- Solder alloy and compliance: lead-free (for example SAC 305) or tin-lead, plus RoHS or other compliance needs.
- Special processes: conformal coating, press-fit, potting, underfill, cleaning or cleanliness requirements.
- Quantities and dates: the quantity breaks you want quoted, the expected annual volume if the build will repeat, and what one finished unit contains (for example, two LED boards for every control board).
Revision control
- Every file carries the same revision label, and the package arrives as one release.
- For a re-spin, include notes listing what changed since the last revision.
Gerber vs. ODB++ vs. IPC-2581
| Format | What it is | Practical notes |
|---|---|---|
| Gerber + NC drill | The long-standing standard: one image file per layer, plus separate drill files | Accepted everywhere. Many files to keep consistent: a six-layer board needs at least 13 Gerbers. |
| ODB++ | An intelligent format that packages layer, drill, component and netlist data together | Widely supported, and less manual interpretation for the manufacturer |
| IPC-2581 | An open, XML-based IPC standard that combines fabrication, assembly and test data in a single file | Support varies by manufacturer, so confirm before relying on it alone |
| Native CAD | Your design tool's own board file | Some manufacturers accept certain tools; always send a neutral format too |
Building a BOM that won't stall
| BOM field | Why it matters |
|---|---|
| Item / line number | Lets everyone refer to the same line unambiguously |
| Quantity per board | Must equal the number of reference designators on the line |
| Reference designators | Must match the layout and centroid file exactly; one line per unique part, all its locations listed |
| Manufacturer + MPN | The only unambiguous way to buy the right part; a generic description isn't enough |
| Description / value | A human-readable cross-check against the MPN |
| Approved alternates | Keeps the build moving when a part goes out of stock. Passives are notorious for doing this without warning. |
| DNP flag | Marks footprints that stay empty, so nobody buys or places them |
| Moisture sensitivity (MSL) | Flags parts needing controlled handling and baking under IPC/JEDEC J-STD-033 |
The centroid file
The centroid file, also called the pick-and-place or XY file, is what programs the placement machines. For each machine-placed part it gives:
- Reference designator
- X and Y position, with the units and the board origin stated
- Rotation
- Board side (top or bottom)
Rotation conventions differ between CAD tools and part libraries, so check the rotation of polarized parts (diodes, LEDs, tantalum and electrolytic capacitors, ICs, connectors) against the assembly drawing before you send the file.
Mistakes that delay first builds
- Files sent in pieces, or from more than one revision.
- BOM and layout disagree: reference designators on one but not the other, or quantities that don't match.
- Missing or incomplete part numbers, or a manufacturer that doesn't match the MPN.
- No approved alternates for parts that go out of stock.
- Rotation or polarity errors in the centroid file.
- DNP parts not flagged in the BOM and on the drawing.
- Dense boards with no assembly drawing, so reference designators and polarity marks can't be read on the board.
- Quantities that don't define the finished unit. If one unit needs two of one board and one of another, say so, so every board is quoted and built in the right quantity.
- Unstated requirements: no IPC class, workmanship standard, solder alloy or test plan until after the quote.
What DFM review checks
Design-for-manufacturability (DFM) and design-for-assembly review catches problems on screen instead of on the line. At Surface Art it covers:
- Footprints and packages: pads that match the part, for reliable joints.
- Thermal review: parts and copper that will be hard to reflow or rework consistently.
- Test access (DFT): test-point coverage for the planned test methods.
- BOM scrub: part availability, lifecycle status and consistency between the BOM and the design.
- Datasheet review: we check the datasheet for each part on your BOM as part of process review. That's why we ask for the BOM in Excel, with manufacturer part numbers.
Send your package before you release it. We'll return a DFM review with the quote.
Schedule a DFM review →First article inspection
First article inspection (FAI) verifies the first assembled board, or the first few, against the drawing, BOM and centroid data before the rest of the run continues: right parts, right places, right orientation, and workmanship to the specified class. On an NPI build it's where data-package errors that slipped past review get caught, while they're still cheap to fix.
Some industries formalize it. Aerospace programs, for example, commonly require a first article inspection report in the format of SAE AS9102. If your program needs a formal FAI report, say so in the RFQ.
Every package that reaches Surface Art gets DFM, DFT and BOM-scrub review before a single part is placed. That review is a big part of how we hold a 99%+ first-pass yield and keep internal rework under 1%.
Before we quote, we send a short list of clarifying questions and state our assumptions about quantities, scope and requirements, so the quote matches what you actually need to build.
Have Gerbers, ODB++ or a BOM ready? Email them to quotes@surfaceart.com. We'll review the package, send any clarifying questions, and then quote.
Sources
- Duane Benson, "Electronic manufacturing files: what we need for PCB assembly," I-Connect007 SMT007 (December 2018). iconnect007.com
- IPC-2581 Consortium, IPC-2581 open data-transfer standard. ipc2581.com
- IPC/JEDEC J-STD-033, Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface Mount Devices.
- IPC, "IPC releases J revisions of two leading standards for electronics assembly" (April 2024). electronics.org
- SAE AS9102, Aerospace First Article Inspection Requirement.