Important PCB Design Files for PCB Assembly & Fabrication

By Mer-Mar Electronics Date posted: Last updated: January 2, 2023
pcb design files

While a PCB ensures the success of an electronic device, it is possible for the PCB to do so if it is fabricated correctly. To do that it is important that the PCB design files to describe the board specifications correctly. Detailed documentation ensures that there is no guesswork when it comes to fabricating & assembling the boards.

Some of the important PCB design files include Gerber Files, IPC-2581, Netlist, Drill Files, BOM, Fab Drawings, Pick & Place Files & ODB++ Files. Let us look at some of these design output files in detail:

Files Needed for PCB Assembly

1. PCB Gerber Files

These files are generated once the layout design is complete. In fact, Gerber files are generated for every layer of the PCB. Some of the Gerber Files for manufacturing therefore include:

  • Aperture definitions
  • TOP
  • Solder Mask Top
  • Solder Paste Top
  • BOT or bottom layer
  • Solder Paste Bottom
  • Silkscreen Top
  • Silkscreen Bottom
  • Assembly Top
  • Assembly Bottom, and more

It is the complexity of the board that determines the number of files created.

Files Needed for PCB Fabrication

1. ODB++ Files

Simply put, these files help designers combine all information as also run the necessary manufacturability tests. An intelligent file, it consists of material stack-up, bill of materials, component placement and more, in a single file. Unlike a Gerber file, the ODB++ Files include a large amount of data and also take away the possibility of human errors.

2. Bill of Materials (BOM)

An extremely important file, it contains a list of all the components required in the PCB. Some of the other crucial information mentioned in the PCB BOM includes:

  • Description of parts
  • The quantity required
  • Manufacturer Part Number
  • Footprint of the component
  • Any notes or comments

3. FAB Drawings

These offer manufacturing details of the PCB. Some of the information includes:

  • Board Dimensions including the length, width & thickness
  • Board Outline- It is imperative that for denser boards that have buried vias, additional outlines be added.
  • Drill Details- It needs to include the different drills used such as laser holes, micro via, via on pad, plugged via, blind via & buried via.
  • Stack-up details including
    • Finished PCB thickness- Typically the finished PCB thickness is 62 mils
    • Prepeg thickness- This is dependent on adjacent layers
    • Copper thickness- Typically the thickness of the plating ranges from 20 to 100 microinches
    • Copper cladding thickness- This largely is contingent upon the strength of the current
  • Copper trace & etching tolerance
  • Class of fabrication
  • Color of solder mask
  • Color of silkscreen
  • Impedance Traces, and more

4. Drill Files

With drilling being an expensive as well as an irreversible process, a drill file has a lot of importance. It indicates the position, the size as well as the number of holes in the PCB. The drill holes can be plated or non-plated. Non-plated holes are used as mounting holes. These are also used when the PCB has to be electrically isolated. There are separate files created for plated as well as non-plated holes.

5. IPC-2581

This is a PCB assembly & manufacturing standard. IPC-2581 has a large number of files within a single file. It contains the following information:

  • Layer stack information
  • Material information
  • Test Points
  • Notes for Assembly
  • BOM
  • Netlist in-circuit testing, and more

6. PCB Netlist

It is a list of networks that determine the board’s connectivity interconnection. A PCB netlist performs several functions. Firstly, it is possible to map the designer’s netlist with the manufacturer’s netlist. Customer netlist is also used for electrical validation of the PCB.

7. Pick & Place Files

With most PCB assembly processes being automated & using pick & place machines, Pick & Place files have a special importance. It offers information about the position as well as the orientation of components. Some of the information mentioned in Pick & place files include:

  • Location of components
  • Reference Designators
  • Orientation of components
  • Placement on top or bottom of the board, and more

To Sum Up

Detailed data received from designers can go a long way in ensuring that the PCBs are fabricated & assembled to perfection.  In the absence of this detailed data, there are chances of costly errors at a later stage.

Due emphasis paid at the design stage & effective communication with the manufacturer can go a long way in ensuring that the PCBs are efficient. You can contact Mermar Electronics who communicate with you regarding all files details before starting PCB process so you can avoid costly errors. Contact Mermar Electronics at sales@mermarinc.com or fill out form below to request a free quote.

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