Mechanical Layer

This Gold Phoenix PCB Knowledge Center article explains the requirements and best practices for the mechanical layer in PCB design data.

RECOMMENDATION: Always include a Gerber mechanical layer in your data set.

IMPORTANT:

• A proper mechanical layer is vital to a good and flawless production of the PCB, as it should provide all the needed mechanical information for the construction of your PCB.

• In case of cut-outs or slots in your PCB, this layer is essential to the production.

• DO NOT scale your mechanical layer; it should be 1:1 and reflect the exact dimensions of the PCB.

• The mechanical layer is — as for all layers — also viewed from top to bottom through your PCB, so do not mirror the mechanical layer.

• ONLY include information in your mechanical layer that is needed.

1. Minimum Mechanical Layer Contents

A mechanical layer should minimally contain:

• The exact board outlines, ideally including dimensions (mm or inch)

• Exact positions and sizes for all inside milling, slots or cutouts, ideally including dimensions (mm or inch)

Outlines are best shown using a small line — e.g., 0.50 mm (20 mil) wide — where the center of the line represents the exact board outline.

IMPORTANT: When no dimensions are given, the center of the contour lines will always be taken as the exact outline of the board, regardless of their thickness.

2. Additional Information When Needed

Additional information that should be included in the mechanical plan when needed:

• A reference hole: The distance from one drill hole in X and Y to the PCB outline. This is particularly important when you only have NPTH (non-plated through hole) holes without copper pads.

• Positional indication of all drills using symbols (= drill map). Use different symbols for each different drill size.

• PTH/NPTH indication for holes and slots

• If you supply panelized data, include proper indications for break-routing and/or scoring (V-cut)

• A clear layer sequence or buildup drawing including all copper layers, solder mask and legend layers, any additional layers like peel-off or carbon, in the correct sequence viewed from top to bottom and with the correct corresponding data file name

3. Non-Poolable Option

Special build-up: If the build of your PCB requires material thicknesses, copper thicknesses or multilayer buildups which are different from standard values, then add this information to the layer sequence or buildup drawing.

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