Sending a PCB manufacturer only the PCB layout file is usually not enough to start production.
A manufacturer needs a set of fabrication data that clearly defines the finished board. The more complete and consistent the information is, the less time is spent asking questions about dimensions, materials, holes, copper layers or special requirements.
The exact file package varies between manufacturers, but most PCB projects require several key pieces of information.
Gerber files are one of the main data formats used to manufacture PCBs.
They normally contain the individual PCB layers, such as copper, solder mask and silkscreen. A board outline is also required.
For a multilayer PCB, each copper layer should be clearly represented.
Before sending the files, it is useful to open them in a Gerber viewer and check that the layers appear correctly.
The manufacturer also needs information about the holes in the PCB.
Drill data defines the locations and sizes of drilled holes. Depending on the design, the file package may contain information for plated holes, non-plated holes and other drilling features.
Small holes, slots and special via structures should be checked carefully because they may require specific manufacturing capabilities.
The manufacturer needs to know how many layers the PCB has.
For example, a four-layer board requires a different manufacturing process from a two-layer board.
For multilayer PCBs, simply stating the layer count may not be sufficient. The manufacturer may also need the intended layer arrangement and material construction.
A PCB stackup describes how the layers are arranged within the board.
It can include copper thickness, dielectric materials and dielectric thickness.
Stackup information becomes particularly important for controlled-impedance designs and high-speed PCBs.
If the impedance requirements are critical, the manufacturer needs enough information to produce the physical structure required by the design.
The PCB material should be specified clearly.
FR-4 is widely used, but different applications may require different material properties.
The required material may be defined by the laminate family, thermal performance, dielectric characteristics, Tg or other specifications.
Simply writing “FR-4” may not provide enough information for a demanding application.
Copper thickness should be specified for the PCB layers where it matters.
The required copper thickness can affect current-carrying capability, resistance, thermal performance and manufacturing conditions.
For high-current designs, this information becomes particularly important.
The manufacturer needs the finished PCB dimensions and required board thickness.
The board outline should be clearly defined in the fabrication data.
If the PCB contains unusual shapes, slots, cutouts or edge features, these should be included in the manufacturing documentation.
The required PCB surface finish should also be specified.
Common options include HASL, lead-free HASL, ENIG, OSP and other finishes.
The choice can depend on component requirements, soldering conditions, environmental considerations and the intended application.
The manufacturer needs to know the required solder mask configuration and silkscreen information.
The fabrication files normally define the locations of these features.
It is also useful to check that reference designators and other silkscreen markings do not overlap component pads or other areas where they cannot be printed correctly.
A fabrication drawing can provide information that may not be obvious from the Gerber files alone.
It can specify board thickness, dimensions, tolerances, material, copper weight, surface finish, special holes and other manufacturing requirements.
For simple boards, some manufacturers can work primarily from the standard fabrication files. For more complex boards, a detailed fabrication drawing can reduce ambiguity.
If the PCB contains controlled-impedance traces, the manufacturer needs the required impedance values and the relevant signal layers.
The manufacturer may use the supplied stackup and trace geometry to control the finished impedance.
For high-speed designs, impedance information should not be left as an assumption.
Some boards contain requirements that are not part of a standard PCB order.
Examples include:
Blind or buried vias.
Back drilling.
Via filling.
Edge plating.
Castellated holes.
Special copper thickness.
Tight dimensional tolerances.
These requirements should be clearly documented before production.
Revision control is easy to overlook but extremely important.
A PCB project may have several versions of the Gerber files, fabrication drawing and other documents.
The manufacturer should be able to identify which revision is approved for production.
Using consistent revision numbers across the documentation helps prevent an older file from accidentally being manufactured.
For a typical PCB fabrication project, the manufacturer may need:
Gerber files + drill files + board specifications + stackup information + fabrication drawing + special requirements + revision information
The exact package depends on the complexity of the board and the manufacturer's data requirements.
PCB fabrication and PCB assembly require different information.
If the manufacturer will also assemble components, additional files are normally required, such as the BOM, pick-and-place file and assembly drawing.
The BOM identifies the components, while the placement data defines where those components are installed.
Keeping the fabrication files and assembly files synchronized is important when a PCB design is revised.
The best time to find missing information is before production starts.
Check that the Gerber files match the intended PCB revision, drill data is complete, the board dimensions are correct, the stackup and material requirements are clear, and any special manufacturing features are documented.
A complete manufacturing package gives the PCB manufacturer a much clearer definition of what needs to be built.
It also reduces unnecessary clarification and makes it easier to identify problems before the PCB enters production.
How Can I Tell If a PCB Design Is Ready for Manufacturing?
What Should I Ask a PCB Manufacturer Before Placing an Order?
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