Many PCB assembly quote delays and cost discrepancies are not caused by pricing strategy—but by incomplete or inconsistent documentation. Clean Gerber files, a well-structured BOM, and accurate pick-and-place data are the foundation of fast, accurate PCBA quotes.    This guide explains how to prepare these files correctly and what PCB assembly manufacturers actually look for when reviewing your data.

Why Proper PCBA Documentation Matters

From a manufacturer’s perspective, every missing detail increases risk.    To protect yield and schedule, suppliers often add cost buffers or request clarifications—    slowing down your project. Clear documentation reduces uncertainty and leads to    faster quotes, fewer questions, and smoother production.

1) Gerber Files: The Foundation of PCB Fabrication

What Gerber Files Are Used For

Gerber files define the physical PCB: copper layers, solder mask, silkscreen,    drill locations, and board outline. Even for assembly-only quotes, manufacturers    review Gerbers to understand board size, layer count, and assembly constraints.

Required Gerber Layers

• Top and bottom copper layers

• Inner layers (if multilayer)

• Solder mask (top and bottom)

• Silkscreen (top and bottom)

• Board outline / mechanical layer

• Drill files (plated and non-plated)

Best Practices for Gerber Files

• Use a standard Gerber format (RS-274X)

• Ensure board outline is clear and unambiguous

• Check polarity and alignment of solder mask openings

• Avoid overlapping silkscreen on pads

• Include a readme file describing layer names

2) BOM (Bill of Materials): Where Most Quote Errors Start

What the BOM Is Used For

The BOM drives component sourcing, cost, lead time, and risk.    A poorly structured BOM often results in incorrect assumptions,    substitute parts, or delayed builds.

Essential BOM Columns

• Reference designators (e.g. R1, C5, U3)

• Quantity per board

• Manufacturer name

• Manufacturer part number (MPN)

• Description and key parameters

• Package / footprint

Strong BOM Practices

• Use manufacturer MPNs—not distributor SKUs

• Clearly mark DNI / DNP components

• Group identical components under the same line item

• Specify approved alternates (or explicitly disallow them)

• Lock BOM revision before requesting quotes

3) Pick-and-Place (Centroid) File: Placement Accuracy

What Pick-and-Place Data Is Used For

The pick-and-place file tells assembly machines where and how to place each component.    Errors here can cause misalignment, rotation mistakes, or assembly delays.

Required Pick-and-Place Fields

• Reference designator

• X and Y coordinates

• Rotation angle

• Top / bottom side indication

• Package type

Best Practices for Pick-and-Place Files

• Confirm rotation convention (0°, 90°, 180°, 270°)

• Ensure origin reference is clearly defined

• Remove DNI components from placement data

• Verify polarity-sensitive parts manually

4) Assembly Drawings: Reducing Assumptions

Assembly drawings clarify intent where data files cannot.    They are especially valuable for complex boards or mixed-technology designs.

What to Include in Assembly Drawings

• Top and bottom component placement views

• Polarity and pin-1 markings

• Special handling notes (ESD, moisture-sensitive parts)

• Through-hole and selective solder notes

5) Common Documentation Mistakes That Delay Quotes

• Missing pick-and-place files

• BOM without MPNs

• Unclear board outline or dimensions

• DNI parts not clearly identified

• Inconsistent reference designators across files

Recommended PCBA Quote Package Checklist

• Gerber files (zipped, clearly named)

• BOM (Excel or CSV format)

• Pick-and-place (centroid) file

• Assembly drawings (PDF)

• Testing requirements (AOI, X-ray, ICT, FCT)

• Target quantity and delivery schedule

How Good Documentation Reduces PCBA Cost

Clear documentation lowers risk. Lower risk leads to:

• More accurate pricing

• Fewer engineering questions

• Shorter lead time

• Higher first-pass yield

• Reduced rework and scrap

Conclusion

Accurate PCBA quotes start with accurate data. By preparing clean Gerber files,    a well-structured BOM, and correct pick-and-place data, you enable manufacturers    to quote confidently and build reliably. Investing time in documentation upfront    saves far more time—and cost—later in the PCB assembly process.

FAQ

Can I get a PCBA quote without a pick-and-place file?

Sometimes, but it often slows down quoting and increases risk. Most manufacturers    strongly prefer centroid data for accurate setup estimation.

Should I allow component alternates in the BOM?

Allowing controlled alternates can reduce cost and lead time, but alternates    should be clearly defined and approved in advance.

Is ODB++ better than Gerber?

ODB++ can reduce ambiguity by bundling data into a single package,    but many manufacturers still work very effectively with clean Gerber files.