PCB Copper Layer and Design

1. Generate output files for copper layers

Use “blink” for pads and avoid “draw/draw” pads when generating output data files. For larger copper areas or copper planes, avoid filling them with small paintings (“painting”). Where possible, use contours or polygons to construct areas or planes. Always include board outlines when exporting copper layers, which helps us identify any data alignment, rotation, or mirroring issues.

2. Non-plated through hole (NPTH)

Remove copper pads from NPTH holes if these pads were not used or not connected to other copper prior to generating the output data file.

3. Copper mesh and copper sheet

Check your final design for small areas of unconnected copper or narrow copper meshes and strips, which can cause production issues.

4. Edge gap of copper plate

For wiring boards:

• Outer layer 0.25mm (10mil)
• Inner layer 0.40mm (16mil)

For boards with score (V-cut):

• Outer and inner layers 0.45mm (18mil)

If you need copper areas or planes to extend to the board’s edge, this must be explicitly indicated in the mechanical layer. Copper should only be used up to the edge of the board if necessary because:

• There is a risk of board edge roughness due to possible tearing of the copper during outline routing (outline).
• Copper creates electrical shorts between layers.
• Copper up to the board’s edge is incompatible with scoring (V-cut).

5. Plate edge plating

Please specify if you need to plate the board’s edge or part of it in the mechanical layer. Additionally, if the board edge is the board, copper must be placed on the top and bottom layers with a minimum width of 0.5mm inwards from the board edge.

This is necessary to allow us to produce round-edge plating so that the metallization is physically strong enough to remain attached to the side of the board.

6. Text placed on the copper layer

Any text placed in a copper layer must comply with the design rules for a given category as defined in our PCB Design Guidelines – Category page. All copper text must be properly legible after etching.

Always view the PCB from top to bottom, through the PCB. Therefore, the text on the top layer of the board should be readable, while the text on the bottom layer should be unreadable or mirrored.

7. Avoid “peelable”

“Strippables” occur during production and are small/narrow pieces of photoresist surrounded by pads, traces, and/or planes. These can “flake” during processing and cause shorts or opens.

8. Edge connector

The surface finish for edge connectors is usually so-called hard gold plated over nickel, which allows repeated mating and unmaking of the connector. To help guide edge connectors into sockets, they need to have a chamfered leading edge. The most typical is the PCB golden finger.

9. Sequence

Always provide the correct layer order for multilayer boards. Layer sequences can be given in various ways:

• Indicates the layer number in the copper image by placing a logical number in each layer (1 for the top layer, 2 for inner 1, 3 for inner 2, etc.)
• Make sure the positions of the numbers do not overlap and are visible through the entire PCB.
• Name each layer file to indicate the order to be used (e.g. Top, Inner 1, Inner 2, Bottom).
• Include a clear composition diagram in your mechanical layer files with the correct order and corresponding data file names including all copper layers, solder masks, legend layers, and additional layers such as peel or carbon layers.
• Include a simple ASCII text file with your data indicating which file will be used for which layer, preferably already in the correct build order (this is the least preferred solution).