Arduino Shield Design Overview
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Accessing knowledge base.
Here’s a breakdown of the most common PCB layers you’ll see in Flux (and in most EDA tools), and the role each plays—followed by a focused note on the solder-mask layer.
Table
| Layer Name | Typical Short Name | What It Does |
|---|---|---|
| Top Copper | F.Cu | Carries all top-side copper traces, pads, and fills for signal and power routing. |
| Bottom Copper | B.Cu | Same as Top Copper but on the bottom side. Used for routing, ground pours, or thermal reliefs. |
| Top Solder Mask | F.Mask | Defines where solder mask (the green/blue/etc. protective coating) is not applied on the top. Openings expose pads for soldering. |
| Bottom Solder Mask | B.Mask | Same as Top Solder Mask but on the bottom side. |
| Top Silkscreen | F.SilkS | Contains reference designators, logos, and other text/artwork printed in ink on the top side. |
| Bottom Silkscreen | B.SilkS | Same as Top Silkscreen but on the bottom side. |
| Paste Mask (Top) | F.Paste | Defines solder-paste stencil openings on the top for SMD pads. |
| Paste Mask (Bottom) | B.Paste | Defines solder-paste stencil openings on the bottom. |
| Board Outline | Edge.Cuts | The mechanical outline of the board. Used by the fab house to cut your board to shape. |
| Drill Drawing | Drills | Shows drill locations and sizes for vias and through-holes. |
| Mechanical Layers | e.g. Dwgs.User1 | User-defined layers for mechanical notes, keep-out areas, mounting holes, or assembly drawings. |
| Courtyard/Keep-Out | e.g. Dwgs.User2 | Defines clearances around components that pick-and-place machines respect or that humans use for assembly/inspection spacing. |
The solder mask is the thin, non-conductive polymer coating applied over copper traces and pads to:
- Prevent solder bridges between adjacent pads or traces during reflow.
- Protect exposed copper from oxidation and contamination.
- Provide a professional finish and insulation for the board.
In Flux, the Top Mask (F.Mask) and Bottom Mask (B.Mask) layers let you control exactly which copper areas are exposed (pad openings) and which are covered with mask.
Toggle mask visibility
Add manual mask openings
Set mask expansion
Configure paste openings
Enable via tenting
227 days
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