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Drilling program

A drilling program is used to communicate the required holes on a printed circuit board to the PCB manufacturer. The drilling program is exported from as Excellon or Sieb & Meyer from the circuit board layout software and usually accompanies Extended Gerber data (RS-274X).

The drilling program itself is an ASCII text file defined by the IPC NC-349.

Preferable is the Excellon and Sieb & Meyer 3000 (SM3000) format as they already have the aperture table (diameter of the holes) integrated. The format SM1000 is not recommended (extra aperture table).

Since the metric system has become established in the production of circuit boards for drilling, the drilling program should be output as metric data. The formats 3.3 leading mm or 4.4 leading mm have proved their worth. That is, a coordinate is given in mm and has 3 places in front and 3 places after the decimal point at 3,3 leading, and 4 places each at 4,4 leading. The commas are not displayed in the finished drilling program!

Especially with the 2.3 inch resolution, problems with hole positioning can occur if the Gerber data has been output in a higher resolution. For each type of hole (for example, through-plated, non-plated-through, blind holes, ...) a separate drill file should be exported.

Beispiel für eine Excellon Datei:

M48Start of file
VER,1Use X- and Y-axis Version 1
FMAT,2Use commands according to type Format 2
METRIC,LZmetric data, leading zeroes
T1C.2Tool 1, diameter: 200µm
T2C.9Tool 2, diameter: 900µm
T3C1.2Tool  3, diameter: 1200µm
%Initialise machine
T1Use tool 1
X02014Y01090Drill coordinate
X03623Y01478Drill coordinate
X03704Y01784Drill coordinate
T2Use tool 2
X00675Y01705Drill next coordinate
M30End program / rewind

See also PCB data formats - Gerber, or find information on Wikipedia.

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