PCB Assembly File Requirements Explained: Gerber, BOM, and Pick-and-Place

Submitting correct and complete files is essential for fast and accurate PCB assembly. Missing or incorrect data often leads to delays, extra costs, and manufacturing errors.

Dans ce guide, TOPFAST, a professional PCB manufacturer, explains all PCB assembly file requirements, how each file is used, and how to prepare them correctly.

Why PCB Assembly Files Matter

Accurate files help manufacturers:

• Understand your design intent
• Prevent assembly errors
• Shorten the lead time
• Reduce engineering questions

Well-prepared files enable smooth turnkey PCB assembly.

Guide connexe :
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Required Files for PCB Assembly

Most PCB assembly manufacturers require the following files:

1. Fichiers Gerber
2. Nomenclature (Bill of Materials)
3. Pick-and-Place (CPL) file
4. Assembly drawings (recommended)

Let’s review each one in detail.

Fichiers Gerber

What Are Gerber Files?

Fichiers Gerber describe the physical layout of the PCB, including copper layers, solder mask, silkscreen, and board outline.

Typical Gerber Files Include:

• Top & bottom copper layers
• Solder mask layers
• Silkscreen layers
• Drill file
• Board outline

Best Practices:

• Use RS-274X format
• Clearly define layer polarity
• Ensure correct board outline

Article connexe :
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Nomenclature (Bill of Materials)

What Is a BOM?

A BOM lists all components required for assembly.

A Complete BOM Should Include:

• Reference designator (e.g., R1, C2)
• Component description
• Manufacturer part number (MPN)
• Quantité
• Package type
• Alternative parts (recommended)

Common BOM Mistakes:

• Missing MPNs
• Inconsistent reference designators
• Outdated or obsolete parts

Accurate BOMs are critical for component sourcing in a turnkey PCBA.

Pick-and-Place (CPL) File

What Is a Pick-and-Place File?

The Pick-and-Place file (also called CPL or centroid file) tells assembly machines:

• Component coordinates
• Angles de rotation
• Placement side (top/bottom)

CPL File Requirements:

• Correct origin point
• Accurate rotation values
• Consistent reference names

This file is essential for SMT PCB assembly.

Article connexe :
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Assembly Drawings (Highly Recommended)

Although optional, assembly drawings greatly improve accuracy.

They can include:

• Component orientation notes
• Polarity markings
• Special assembly instructions
• THT or hand-soldering notes

Assembly drawings help reduce engineering questions.

Additional Files for Advanced PCBA

Depending on the project, manufacturers may also request:

• Test requirements or test programs
• Programming files
• Instructions spéciales pour le processus
• Functional test specifications

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File Checklist Before Submission

Before submitting files, verify:

• All reference designators match across files
• BOM quantities are correct
• CPL file aligns with Gerber layers
• Special instructions are clearly documented

This checklist helps ensure fast PCB assembly turnaround.

Common File-Related Issues in PCB Assembly

• Mismatch between BOM and Gerber
• Incorrect rotation angles
• Missing polarity indicators
• Incomplete BOM data

These issues can delay production if not addressed early.

File Requirements in Turnkey PCB Assembly

In turnkey PCB assembly, manufacturers rely heavily on accurate files to:

• Source correct components
• Optimize assembly flow
• Perform reliable testing

Article connexe :
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Pourquoi choisir TOPFAST pour l'assemblage de circuits imprimés ?

En tant que fabricant professionnel de circuits imprimés, TOPFAST provides:

• Free file review before production
• DFM/DFA engineering support
• Clear communication on file issues
• Fast turnaround for prototypes and production

Well-prepared files combined with TOPFAST expertise ensure smooth PCBA production.

Conclusion

Correct PCB assembly files are the foundation of successful PCBA production. By preparing accurate Gerber, BOM, and Pick-and-Place files, customers can significantly reduce cost, risk, and lead time.

PCB Assembly File FAQ