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Preparing the right PCB prototype documentation is an important step before sending a design to a PCB manufacturer. A complete and consistent manufacturing package allows the supplier to understand what needs to be fabricated, assembled, inspected, and tested without unnecessary clarification.
For a bare PCB prototype, the package normally includes Gerber files, drill data, and fabrication information. If PCB assembly is required, additional files such as the BOM, pick-and-place data, and assembly drawings are needed.
The goal is not to send as many files as possible. The goal is to provide one complete and consistent set of manufacturing data.
PCB Prototype Documentation Checklist
Before submitting a PCB prototype for quotation or production, check that your package includes the following files:
| File | Main Purpose |
|---|---|
| Gerber Files | Define PCB copper, solder mask, silkscreen, and other fabrication layers |
| NC Drill Files | Define plated and non-plated holes |
| Fabrication Drawing | Defines board specifications and manufacturing requirements |
| BOM | Identifies components, quantities, and part numbers |
| Pick-and-Place File | Provides component coordinates, rotation, and placement side |
| Assembly Drawing | Shows component locations, polarity, orientation, and special notes |
| Test Requirements | Defines electrical or functional testing when required |
| Revision Information | Keeps all manufacturing files synchronized |
Not every prototype requires every file. For example, a bare PCB order does not normally require a BOM or pick-and-place file. However, a PCBA prototype requires a much more complete documentation package.
1. Gerber Files
Gerber files are the primary fabrication data used to manufacture the bare PCB.
Depending on the board design, the Gerber package may include:
- Copper layers
- Solder mask layers
- Silkscreen layers
- Paste layers when required for assembly
- Board outline
- Additional fabrication layers
Before sending the files, open the complete Gerber package in a viewer and verify that all required layers are present and aligned correctly.
The board outline is particularly important because it defines the physical dimensions and manufacturing boundary of the PCB.
2. NC Drill Files
The NC drill file defines the locations and sizes of drilled holes.
It may include:
- Through-hole vias
- Component holes
- Mounting holes
- Plated holes
- Non-plated holes
- Slots, depending on the manufacturing data format
Make sure the drill data matches the Gerber files and that plated and non-plated features are clearly identified when required.
A mismatch between the drill file and the PCB artwork can create engineering questions before production begins.
3. PCB Fabrication Drawing
A fabrication drawing provides manufacturing information that may not be completely defined by the Gerber files.
Depending on the project, it can specify:
- Board thickness
- Layer count
- Material
- Copper weight
- Surface finish
- Solder mask color
- Board dimensions and tolerances
- Controlled impedance requirements
- Special holes or slots
- Edge plating
- IPC class
- Other manufacturing notes
This document is especially useful for prototypes with non-standard requirements.
For example, if the design requires controlled impedance or a specific high-Tg material, that requirement should be clearly documented rather than left to interpretation.
4. Bill of Materials (BOM)
A BOM is required when the prototype includes component assembly.
A useful BOM should identify each component clearly and typically include:
- Reference designator
- Quantity
- Manufacturer
- Manufacturer Part Number (MPN)
- Package
- Component description
- Approved alternatives when applicable
Avoid using only generic descriptions such as “10 kΩ resistor” when an exact component is required.
An accurate MPN allows the manufacturer or assembler to verify component availability, package information, and sourcing requirements.
5. Pick-and-Place File
The pick-and-place file, also called a centroid or XY file, provides the automated placement information for SMT components.
Typical information includes:
- Reference designator
- X coordinate
- Y coordinate
- Rotation
- PCB side
- Units
The coordinate origin and rotation convention should be consistent with the PCB design data.
A common problem occurs when the BOM, pick-and-place file, and assembly drawing come from different revisions of the design.
6. Assembly Drawing
An assembly drawing provides a visual reference for component placement.
It can help the assembly team verify:
- Component locations
- Component orientation
- Polarity
- Pin 1 indicators
- Reference designators
- Top and bottom assembly
- Special assembly instructions
- DNP (Do Not Populate) components
For complex PCBA prototypes, the assembly drawing provides an additional layer of verification that cannot be obtained from the BOM alone.
7. Test and Inspection Requirements
If the prototype requires specific testing, include those requirements with the manufacturing package.
Depending on the project, this may include:
- Electrical testing
- Flying probe testing
- Functional testing
- AOI
- X-ray inspection
- Impedance testing
- Programming
- Special inspection criteria
The manufacturer should know these requirements before quotation because testing can affect process planning, tooling, cost, and lead time.
8. Revision Control: Make Sure Every File Matches
One of the most important parts of PCB prototype documentation is revision consistency.
For example:
Gerber: Rev B; BOM: Rev A; Pick-and-place: Rev B
This creates uncertainty about which design should actually be manufactured.
Before submitting a prototype, confirm that:
- Gerber files use the correct revision
- Drill files match the same revision
- BOM matches the PCB design
- Pick-and-place data matches the BOM
- Assembly drawings match the current component placement
- Fabrication notes reflect the current requirements
A simple revision-control check can prevent unnecessary engineering clarification and production delays.
9. Include a Readme or Manufacturing Notes When Necessary
For complex prototypes, a short README or manufacturing note can make the package easier to review.
It can identify:
- Project name
- PCB part number
- Revision
- Required quantity
- Bare PCB or PCBA
- Special materials
- Surface finish
- Controlled impedance requirements
- Testing requirements
- Approved substitutions
- Special packaging instructions
The purpose is not to duplicate information already contained in the manufacturing files. It is to highlight requirements that could otherwise be misunderstood.
PCB Prototype Documentation: Bare PCB vs. PCBA
The required documentation depends on what you are ordering.
| Requirement | Bare PCB Prototype | PCBA Prototype |
|---|---|---|
| Gerber Files | ✓ | ✓ |
| NC Drill | ✓ | ✓ |
| Fabrication Drawing | Recommended | ✓ |
| BOM | — | ✓ |
| Pick-and-Place | — | ✓ |
| Assembly Drawing | — | ✓ |
| Test Requirements | If required | If required |
| Programming Data | — | If required |
| Special Assembly Notes | — | If required |
A PCBA prototype therefore requires both PCB fabrication data and assembly data.
Common PCB Prototype Documentation Mistakes
Sending Different Design Revisions
This is one of the easiest mistakes to make and one of the most disruptive during manufacturing.
Missing Board Outline
Without a clearly defined board outline, the manufacturer may need clarification before fabrication.
Incomplete BOM
Missing MPNs, quantities, reference designators, or approved alternatives can delay component sourcing.
Incorrect Pick-and-Place Data
Incorrect coordinates, rotation, units, or PCB side information can result in incorrect component placement.
Important Requirements Only Mentioned in Email
Critical requirements such as material, impedance, surface finish, or special testing should be included in the formal manufacturing documentation rather than relying only on email instructions.
How to Prepare PCB Prototype Documentation Before Quotation
A practical preparation workflow is:
Finalize PCB Design → Run DRC → Export Gerber and Drill Files → Prepare Fabrication Drawing → Prepare BOM and Pick-and-Place→ Data if Assembly Is Required → Check Revision →Consistency → Review Manufacturing Package → Submit for Quotation
This process gives the manufacturer a consistent set of information before engineering review begins.
Final PCB Prototype Documentation Checklist
Before sending your prototype files, confirm:
- All required Gerber layers are included
- Board outline is clearly defined
- NC drill files are included
- Fabrication requirements are documented
- Material and surface finish are specified
- BOM includes accurate part information
- Pick-and-place data matches the current PCB revision
- Assembly drawing is included when PCBA is required
- Test requirements are clearly defined
- All files use the same revision
- Manufacturing notes contain critical special requirements
Conclusion
Good PCB prototype documentation reduces uncertainty between the PCB designer and manufacturer. Gerber files and drill data define the physical board, while fabrication drawings communicate manufacturing requirements. For PCBA prototypes, the BOM, pick-and-place file, and assembly drawing provide the additional information needed for component sourcing and assembly.
The most important principle is consistency. Every file should describe the same PCB revision and the same manufacturing intent.
By checking the documentation package before quotation, engineers can reduce clarification cycles, avoid incorrect manufacturing assumptions, and move from PCB design to prototype production more efficiently.
