All performed by CNC machines.
PCB drilling machines can either be programmed optically or directly from the CNC
outputs from the modern cad systems. Or if necessary CNC Data can often
be extracted from the Gerber photoplot Data files.
If both plated and unplated holes are required say for mounting holes or
similar please advise separately from the data files as this information
isn't always carried through from the CAD systems automatically.
Our favourite format for the data is
imperial Excellon 2-3 format but we are quite used to most variants and
have written software to convert other file formats.
The drills we stock are all metric and start off
with 0.05mm size increments which raise to 0.1mm increments for the
larger sizes. All imperial sizes from the CAD systems are converted to
the nearest larger size. To achieve the correct final size for PTH or
Multi Layer Boards we by default increment drill sizes by 0.1mm.
Small point to note is that holes tend to
be a little undersize. This is due mainly to the heat generated during
drilling. This causes a small amount of hole shrinkage. Another factor
is that drills are often made to a minus tolerance. The net result is
that a 1.00mm hole could well measure 0.98mm. Sometimes it can be
demonstrated in extreme cases by the fact that a drill will not easily
fit back into the hole it has just drilled.
Full documentation of the Std Excellon machine
language can be found at
Commercial CNC PCB drilling machines vary in size the photo below is of a 12
spindle one from
TECHNOLOGY it weighs 15000kg and measures 4.4m x 2.15m x 2.13m,
requires a 15KVA power supply and has spindles that are capable of
200,000 rpm. Too large for our UK production but an impressive machine.
Very posh in comparison with P&M's first drill but a lot has changed
within the industry over the roughly 50 years time difference.