PCB Assembly Files Requirements

At Highleap Electronics, complete file packages enable faster processing and fewer engineering questions. We use your Gerbers + drill to generate fabrication tooling, and your BOM + pick-and-place + assembly drawings to program SMT placement and verify polarity/orientation. This guide helps you prepare data that moves smoothly through manufacturing.

---

1) The Complete File Package

1.1 Essential Files Checklist

Always Required:

• ☐ Gerber files (all layers required for fabrication)
• ☐ Drill files (Excellon format)
• ☐ Bill of Materials (BOM)
• ☐ Pick and place / centroid file (component placement)
• ☐ Assembly drawing (Top/Bottom, polarity, refdes)

Often Required (depending on board and build):

• ☐ Fabrication drawing / fabrication notes
• ☐ Stackup specification (especially for impedance or controlled dielectric)
• ☐ Test requirements (AOI/ICT/functional)
• ☐ Special instructions (programming, coating, handling)
• ☐ Panelization information (if panelized or requires rails)

1.2 File Revision Consistency

Critical: All files must be from the same design revision (Gerbers, drill, BOM, pick-and-place, drawings).

Mixed revisions commonly cause:

• Components placed on wrong pads (footprints changed but placement file not updated)
• BOM/placement mismatch (missing parts or wrong quantities)
• Wrong footprints built (Gerber vs drawing vs BOM inconsistency)

Best practice: include a revision identifier in all file names and documents (e.g., RevA / RevB, date stamp, ECO number).

1.3 File Format Summary

---

2) Fabrication Data Requirements

2.1 Gerber Files

Required layers (typical):

• Top copper
• Bottom copper
• Internal copper layers (if multilayer)
• Top solder mask
• Bottom solder mask
• Top silkscreen
• Bottom silkscreen (if used)
• Board outline / profile (required)

Recommended (when applicable):

• Mechanical layers for cutouts, slots, routing depth, edge plating notes
• Fabrication layer / drawing references (if your CAD outputs them as Gerbers)

Gerber specifications:

• Format: RS-274X (embedded apertures) or Gerber X2
• Units: Metric preferred; imperial acceptable (do not mix units across layers)
• Ensure consistent polarity and correct layer naming
• Include a clear, unambiguous board outline layer

2.2 Drill Files

Required:

• Plated through holes (PTH)
• Non-plated holes (NPTH) as a separate file (recommended)
• Tool table (drill sizes + counts)

If applicable:

• Blind via drill files
• Buried via drill files
• Back drill files
• Slots / routing definitions (if not captured elsewhere)

2.3 Fabrication Drawing / Notes (PDF)

Provide a fabrication drawing (PDF) showing:

• Board dimensions and tolerances
• Layer stackup and thickness
• Material specifications (e.g., FR-4, high-Tg, Rogers)
• Impedance requirements (if any)
• Surface finish (ENIG, HASL, OSP, etc.)
• Solder mask color and silkscreen color (if required)
• Special requirements (edge plating, via fill/cap, controlled depth routing, etc.)

---

3) Assembly Data Requirements

3.1 Pick and Place / Centroid File

For detailed formatting and conventions, see pick-and-place-file-requirements.

Required columns:

• Reference designator (must match BOM)
• X coordinate
• Y coordinate
• Rotation
• Side (Top/Bottom)

Include in header notes (to avoid common failures):

• Units (mm or mils)
• Origin location (lower-left of outline or board center—state it clearly)
• Rotation convention (CCW positive or otherwise)
• Bottom-side handling (mirrored or not)
• Board revision matching Gerbers and BOM

See also: Centroid file specifications.

3.2 Solder Paste (Stencil) Gerbers

• Top paste layer (required for SMT)
• Bottom paste layer (if bottom-side SMT)

Note: Paste layers define stencil openings. Stencil apertures may be modified for print quality and yield per stencil aperture guidelines.

3.3 Assembly Drawing (PDF)

Provide an assembly drawing (PDF) showing:

• Component placement (all reference designators visible)
• Component outlines
• Polarity indicators (Pin 1, cathode marks, electrolytic polarity)
• Top and bottom views
• Any special assembly notes (hand-solder, glue, selective solder, etc.)

Submit Your File Package

---

4) Bill of Materials (BOM) Specifications

4.1 Required BOM Columns

4.2 Optional But Helpful Columns

• Populate (Y/N) or DNP/DNI: clearly mark parts not to be assembled
• Alternate MPN (AVL/AML): approved alternative parts and priority
• Distributor and Distributor PN: preferred sourcing
• Value: component value (10K, 100nF)
• Notes: special instructions (orientation constraints, hand-solder, etc.)

4.3 BOM Best Practices

• One line per unique part (group identical components)
• Use complete manufacturer part numbers (avoid partial codes)
• Clearly mark DNP/DNI items (and ensure they are also removed from placement if required)
• Specify approved alternates (or state “no substitutes”)
• Match reference designators exactly to other files

---

5) Supporting Documentation

5.1 Test Requirements

Specify testing expectations:

• Visual/AOI inspection requirements
• ICT or flying probe testing
• Functional test requirements (procedure, pass/fail criteria, fixtures if any)
• X-ray inspection (for BGAs/QFNs when needed)

See Design for Testability for DFT guidelines.

5.2 Special Instructions

Document any special requirements:

• Programming requirements (who provides firmware, programming method, programming header)
• Conformal coating specifications (type, thickness, masked areas)
• Special handling requirements (ESD, moisture sensitivity, baking)
• Workmanship class (IPC-A-610 Class 2 or Class 3; if not specified, confirm the default for your build)

5.3 Panelization Information

If customer-panelized, provide:

• Panel Gerbers (not just individual board)
• Panel array configuration (rows/columns, rails, fiducials)
• Depaneling method (V-score, tabs, router) and any keep-outs

See Panelization requirements for SMT.

---

6) File Submission Best Practices

6.1 File Organization

Recommended folder structure:

ProjectName_RevA/
├── Gerbers/
│   ├── ProjectName_Top.gbr
│   ├── ProjectName_Bottom.gbr
│   ├── ProjectName_Drill_PTH.drl
│   ├── ProjectName_Drill_NPTH.drl
│   └── [all layer files]
├── Assembly/
│   ├── ProjectName_BOM.xlsx
│   ├── ProjectName_PnP.csv
│   └── ProjectName_Assembly.pdf
└── Documentation/
    ├── ProjectName_Fab.pdf
    └── ProjectName_Notes.txt

6.2 File Naming Convention

Include in file names:

• Project name or part number
• Revision indicator
• Layer/file type identifier

Example: ControlBoard_RevC_Top.gbr

6.3 Compression and Submission

• Compress all files into a single ZIP archive
• Include a short readme (optional) describing key files, origin/units, and special notes
• Verify all files open correctly in a viewer before sending
• Use file transfer for large packages (>25MB)

6.4 Pre-Submission Checklist

• ☐ All files are the same revision
• ☐ Reference designators match across files
• ☐ BOM component count matches placement file (placed parts)
• ☐ Gerbers verified in a viewer (outline, polarity, masks)
• ☐ Drill files include tool table and clear PTH/NPTH separation
• ☐ Units and origin are specified (especially for pick-and-place)
• ☐ Special requirements documented (programming, coating, class, test)

6.5 Highleap File Processing

When you submit files to Highleap Electronics:

1. Files received and logged
2. Free DFM review performed
3. DFM report provided
4. Questions clarified before production
5. Production proceeds with verified data

Complete, well-organized files accelerate this process. Review our PCB DFM checklist and assembly design rules before submission.

Contact our engineering team with any questions about file requirements for your specific project.