•Professional manufacture of PCBs is typically done through the use of CAD-independent files:
–Gerber Files – describe the copper foil layout
–Drill Files (often in the Excellon format) – describe the location and size of holes
•Both are meant for direct use with automated PCB production equipment.
•Exellon Drill File
•Excellon Files provide a command sequence to a system that drills PCBse
•This equipment (or its computer driver) has an interpreter that receives and executes the commands in sequence.
•The next two slides describe the list of commands that are interpreted.
Source: “Norme Excellon”, available at http://www.forelec.ch/www/norme_excellon.htm, accessed 12 Feb 2008 (dead link at 26 Jan 2011).
Excellon file format is governed by ANSI/IPC-NC-349 .
% Rewind and Stop
X#Y# Move and Drill
T# Tool Selection
M30 End of Program
M00 End of Program
M25 Beginning of Pattern
M31 Beginning of Pattern
M01 End of Pattern
M02 X#Y# Repeat Pattern R#M02X#Y# Multiple Repeat Pattern M02 X#Y# M70 Swap Axis
M02 X#Y# M80 Mirror Image X Axis M02 X#Y# M90 Mirror Image Y Axis M08 End of Step and Repeat
N# Block Sequence Number
/ Block Delete
R#X#Y# Repeat Hole
G05, G81 Select Drill Mode
G04 X# Variable Dwell (ignored)
G90 Absolute Mode
G91 Incremental Mode
G92 X#Y# Set Zero
G93 X#Y# Set Zero
M48 Program Header to first "%"
M47 Operator Message CRT Display
M71 Metric Mode
M72 English-Imperial Mode
Snn Spindle Speed (RPM)
Fnn Z axis feed speed (IPM)
Typically, only a subset of these commands are used.
File Formats: Excellon Drill File Example
% Reset and rewind.
M48 Start of header.
M72 Imperial (English) Mode: units in inches
T01C0.0420 Tool 1 Change: to 42 mil
T02C0.0860 Tool 2 Change: to 86 mil T03C0.0350 :
T08C0.1520 Tool 8 Change: 152 mil
% End of Header: Drill data follows
T01 Select Tool 1 (42 mil)
X2120Y1112 Drill at (2120 mil,1112 mil)
: (Lots of data removed)
T08 Select Tool 8 (152 mil)
X3645Y262 Drill at (3645 mil, 262 mil)
: (Data removed)
M30 End of program.
•Sample of a drilling machine doing its job: