+44 (0)1495 320 989

Specifying a PCB

In order for Swan EMS to make your board we will need your Gerber files (including the board outline) and the drill files. Alternatively we can generate this all from an Easy PC 14 (or earlier)“.pcb” file

Gerber files

There should be a Gerber file per layer and each Gerber file should have the board outline in it. There should also be drill files for where the holes go

An example of the Gerbers and drill files we need can be seen below:

   "xxxxxx-111211 - Top Silk.gbr"

    "xxxxxx-111211 - Top Copper.gbr"

    "xxxxxx-111211 - Top Copper (Resist).gbr"

    "xxxxxx-111211 - Top Copper (Paste).gbr"

    "xxxxxx-111211 - Bottom Copper.gbr"

    "xxxxxx-111211 - Bottom Copper (Resist).gbr"

    "xxxxxx-111211 - Bottom Copper (Paste).gbr"

    "xxxxxx-111211 - Bottom Silk.gbr"

    "xxxxxx-111211 - Drill Data - Through Hole.drl"

    "xxxxxx-111211 - Drill Data - Through Hole (Unplated).drl"

    "xxxxxx-111211 - Drill Ident Drawing - Through Hole.gbr"

This is for a double sided surface mount board, More layers need more files (for each layer), simpler designs have less. PCB design packages have different ways of presenting these files, as long as we have the right layers and we can tell them apart this will be ok for production.

If you have to make a change to your board, please re-issue all files to prevent any possibility of confusion.


Board Properties

In addition to the design information we also need to specify the board properties

To enable us to make the PCB to the exact specification we will need to know:




Board material

FR4, MF4

FR4 (Fire Retardant 4) is the standard material. When specifying anything else be as precise as possible, e.g. for IMS boards material, manufacturer, substrate thickness etc..



Green as standard

Number of layers


1,2 and 4 most common


0.8mm, 1.6mm etc …

Thicknesses in steps of 0.8mm, this is the thickness of the actual board

Plated through hole


We recommend PTH as standard, with the exception of very low cost single sided PCBs.

Copper thickness

1oz (35um), 2oz (70um) etc..

1 oz copper (1oz of copper per square foot of PCB)  is standard, for higher conductivity or for improved thermal performance use 2oz

Solder Resist

Green, both sides

This is the coating that prevents solder going onto the tracks, except where it is required on the pads. Please specify if its needed both sides

Silk Screen

White,  topside

This is used to identify components, boards need not have silkscreen and its unusual to have it both sides.


None, gold, silver

Platings recommended only for special boards or for edge connectors.

Fire Retardance


Board self extinguishes in the event of being set on fire. This is recommended.

Electrically Tested


Most boards are manufactured perfectly without the need for test, high value complex boards may warrant testing, there is a set up charge.

Specifications in italics are the most likely options and will do for the majority of boards

An example may be “Green FR4, 1.6mm, 1oz copper, double sided, PTH, White silk screen top only , green solder resist both sides, no plating, not electrically tested, UL94-V0” 

Swan EMS have dealt with many Gerber files from many software packages, we are happy to check that we can read them and to advise you on board specifications.

Return to PCB Assemblies