When an electronics company chooses a turnkey PCBA service, one of the first questions is: What files do I need to provide to the PCB assembly factory?
Providing complete and accurate manufacturing files is one of the most important steps before PCBA production begins. The right files allow the manufacturer to understand your PCB design, source the correct components, program SMT equipment, assemble the board correctly, and perform the required inspections and tests.
For most turnkey PCBA projects, the essential documents are Gerber files, BOM (Bill of Materials), and Pick-and-Place/Centroid files. Depending on the complexity of the product, additional documents such as assembly drawings, schematics, test specifications, fabrication drawings, and programming files may also be required.
This guide explains exactly what files you should prepare when requesting turnkey PCB assembly from a Chinese PCBA manufacturer.
What Does Turnkey PCBA Mean?
Before discussing the files, it is useful to understand what “turnkey PCBA” means.
In a turnkey PCBA service, the manufacturer takes responsibility for most or all of the production process, including:
- PCB fabrication
- Component sourcing
- Component inspection
- SMT assembly
- Through-hole assembly
- PCB inspection
- Testing
- Final assembly or packaging, when required
Instead of purchasing components yourself and sending them to the factory, you provide the manufacturing data and the PCBA supplier manages the procurement and production process.
Because the factory is responsible for purchasing and assembling the components, accurate manufacturing documentation is critical.
1. Gerber Files — Essential for PCB Fabrication
Gerber files are one of the most important files required for a turnkey PCBA project.
Gerber files describe the physical layers of the PCB and provide the information needed by the PCB manufacturer to fabricate the bare board.
A typical Gerber package may contain:
- Top copper layer
- Bottom copper layer
- Inner copper layers for multilayer boards
- Top solder mask
- Bottom solder mask
- Top silkscreen
- Bottom silkscreen
- Board outline
- Paste layers
- Additional fabrication layers
For multilayer PCBs, the complete layer stack-up information should also be provided.
The Gerber files should correspond to the final approved PCB design. If you send outdated Gerbers while the BOM or assembly files reflect a newer revision, manufacturing problems can occur.
Gerber files should include the correct revision
We recommend clearly identifying the PCB revision, for example:
PCB Rev. A / Rev. B / Rev. C
The PCB revision should be consistent across the Gerbers, BOM, assembly drawings, and other production documents.
2. BOM (Bill of Materials) — Essential for Component Purchasing
For turnkey PCBA, the BOM is equally important as the Gerber files because the factory uses it to purchase the electronic components.
A good BOM should contain enough information to identify every component accurately.
Recommended BOM information includes:
| BOM Information | Purpose |
|---|---|
| Reference designator | Identifies component location, such as R1, C5, U2 |
| Quantity | Specifies how many components are required |
| Manufacturer | Identifies the original component manufacturer |
| Manufacturer Part Number (MPN) | Identifies the exact component |
| Description | Provides additional component information |
| Value | Resistance, capacitance, IC type, etc. |
| Package | 0402, 0603, QFN, BGA, etc. |
| Approved alternatives | Allows sourcing flexibility |
| Component notes | Special requirements or specifications |
Why the MPN is important?
A description such as:
10k resistor, 1%
may not be sufficient for reliable procurement.
There can be many manufacturers and different specifications for components with the same basic electrical value.
Providing the Manufacturer Part Number (MPN) greatly reduces the possibility of purchasing the wrong component.
3. Pick-and-Place / Centroid File
The Pick-and-Place file, also called the Centroid file or XY file, tells the SMT machine where each component should be placed.
It typically includes:
- Reference designator
- X coordinate
- Y coordinate
- Rotation
- Component side
- Part number or value
For example:
| Reference | X | Y | Rotation | Side |
|---|---|---|---|---|
| R1 | 25.40 | 18.20 | 90° | Top |
| C1 | 27.10 | 18.20 | 0° | Top |
| U1 | 35.20 | 25.40 | 180° | Top |
The exact format varies depending on the PCB design software.
The PCBA factory uses this information to program the SMT placement machines.
If the Centroid file and BOM do not match, the manufacturer may need to perform an engineering review before production.
4. Assembly Drawings
An assembly drawing provides a visual representation of how components should be installed on the PCB.
It can show:
- Component locations
- Reference designators
- Component orientation
- Polarity
- PCB side
- Special assembly requirements
Assembly drawings are especially helpful for:
- Complex PCBs
- Double-sided assemblies
- Through-hole components
- Connectors
- Mechanical components
- Components with unusual orientations
Although the SMT machine primarily uses the Pick-and-Place file, an assembly drawing gives engineers and inspectors an additional reference for verifying the finished PCBA.
5. Schematic — Highly Recommended
A schematic is not always essential for basic SMT assembly, but it is strongly recommended, particularly for complex electronics.
The schematic helps the PCBA manufacturer understand:
- Circuit functionality
- Component relationships
- Polarity
- Connector functions
- Power circuits
- Signal paths
- Potential BOM inconsistencies
If an engineer discovers something unusual in the BOM or PCB layout, the schematic can help determine whether it is intentional or an error.
For engineering-intensive projects, providing the schematic can significantly improve the manufacturer’s ability to perform DFM and BOM reviews.
6. PCB Fabrication Drawing and Stack-Up Information
For more complex PCB projects, customers should also provide a PCB fabrication drawing.
It may specify:
- Board dimensions
- PCB thickness
- Layer count
- Copper thickness
- Surface finish
- Hole requirements
- Impedance requirements
- Via requirements
- Tolerances
- Special fabrication instructions
For high-speed or multilayer designs, PCB stack-up information can be particularly important.
For example, controlled-impedance designs may require specific dielectric thicknesses and copper configurations.
7. Test Specifications and Test Files
If the PCBA requires electrical or functional testing, the factory will need the relevant test information.
Depending on the project, this may include:
- ICT test requirements
- Flying probe requirements
- Functional test procedures
- Test fixture drawings
- Test software
- Programming files
- Test limits
- Pass/fail criteria
- Test instructions
For a functional test, the factory needs to understand exactly what constitutes a successful board.
For example, the test specification might require verification of:
- Input voltage
- Output voltage
- Current consumption
- Communication interfaces
- Sensor readings
- Digital I/O
- Communication protocols
The more detailed the test requirements, the more accurately the factory can implement production testing.
8. Firmware and Programming Files
Some PCB assemblies contain microcontrollers, memories, FPGAs, or other programmable devices.
In these cases, the factory may need:
- Firmware files
- Bootloader files
- Programming software
- Programming instructions
- Device configuration files
- Programming cables or fixture information
The customer should clearly specify:
- Which component needs programming
- Which firmware version should be used
- Whether programming occurs before or after assembly
- Whether firmware version needs to be recorded for traceability
Programming requirements should be treated as part of the manufacturing process rather than an afterthought.
9. Special Quality and Compliance Requirements
Customers should also provide any specific quality requirements before production.
Examples include:
- IPC assembly class
- RoHS requirements
- REACH requirements
- UL requirements
- Customer-specific quality standards
- Traceability requirements
- Material certificates
- First Article Inspection requirements
- Certificate of Conformance requirements
For industries such as medical, automotive, aerospace, and industrial electronics, documentation requirements can be significantly more extensive.
The PCBA factory should review these requirements before issuing the final quotation.
What Is the Minimum File Package for Turnkey PCBA?
For a typical turnkey PCBA project, we recommend providing at least:
1. Gerber files
For PCB fabrication.
2. BOM
For component sourcing.
3. Pick-and-Place/Centroid file
For SMT placement.
4. Assembly drawing
For assembly and inspection reference.
For more complex projects, also provide:
5. Schematic
6. PCB fabrication drawing
7. PCB stack-up information
8. Test specifications
9. Firmware/programming files
10. Special quality or compliance requirements
Not every project requires every file. A simple PCB may need only the first three or four documents, while a complex industrial or medical PCBA may require a much more comprehensive manufacturing package.
How Should You Organize Your PCBA Manufacturing Files?
Good file organization can prevent unnecessary engineering delays.
A recommended structure is:
Project Name
→ PCB
→ BOM
→ Pick-and-Place
→ Assembly Drawing
→ Schematic
→ Test
→ Firmware
→ Specifications
Use consistent revision numbers throughout the package.
For example:
- PCB_Rev_B
- BOM_Rev_B
- PNP_Rev_B
- Assembly_Rev_B
- Schematic_Rev_B
This helps the manufacturer confirm that all documents belong to the same product revision.
What Happens After You Send the Files?
A professional turnkey PCBA manufacturer should normally perform an engineering review before production.
The review may include:
- Gerber review — checking PCB manufacturability.
- BOM review — checking component availability and lifecycle status.
- BOM-to-Gerb comparison — verifying that components and reference designators match.
- DFM analysis — identifying potential assembly problems.
- Component sourcing — obtaining supplier quotations and checking availability.
- Quotation — providing the complete PCBA manufacturing price.
- Customer approval — confirming the BOM, PCB, price, and production specifications.
- Production — PCB fabrication, component procurement, SMT/THT assembly, inspection, and testing.
This engineering review is particularly important for turnkey projects because the manufacturer is responsible for both component procurement and assembly.
So, what files are needed for turnkey PCBA service?
For most projects, the three core files are Gerber files, BOM, and Pick-and-Place/Centroid files. An assembly drawing is also highly recommended. For more complicated products, customers should provide schematics, PCB fabrication drawings, stack-up information, test specifications, firmware, and special quality requirements.
The most important point is not simply sending more files—it is making sure that all files are complete, accurate, and consistent with the same PCB revision.
A professional Chinese PCBA manufacturer should review these documents before production, identify potential DFM and BOM issues, verify component availability, and clarify any discrepancies with the customer before purchasing materials or starting assembly.
If you are preparing a turnkey PCBA project, providing a complete manufacturing data package from the beginning can help reduce engineering questions, prevent component sourcing mistakes, shorten production lead time, and improve overall assembly quality.
