Board characteristics:

- stacking: 2 layers, solder mask on front and back, silk screen on front
- board material: FR4, thickness 0.8 mm (1/32"), 1 oz copper
- surface finish: ENIG recommended
- via holes: diameter is nominally 10 mil, but any size <= 15 mil can be used
- mechanical tolerances: <= +/- 0.1 mm on all sides

Layer stacking, from top to bottom:

atben-SilkS_Front.gto	Front silk screen
atben-Mask_Front.gts	Front solder mask
atben-Front.gtl		Front copper
atben-Back.gbl		Back copper
atben-Mask_Back.gbs	Back solder mask

Other design files:

atben-PCB_Edges.gbr	Board edges, for routing (Gerber)
atben.dxf		idem (AutoCAD DXF)
atben.drl		Excellon drill file

Interpretation of files:

- for all coordinates, the origin is the lower left corner of the board
- the center (!) of the board edge line marks the true board edge, e.g.,

                             Edge line (5 mil)
                        =======
         ------- - - - - - ----------
               |           |
   PCB outside |           | PCB inside
               |           |
         ------- - - - - - ----------
                     |
               Volume removed when cutting
               (width depends on tool used)