In The Trenches
It’s easier to lay out the board yourself
than to chase down elusive errors
made by a machine.
It is important to do printed circuit
board layout properly. It requires
common sense and attention to
detail. Hopefully, this overview has
provided some insights that will be
useful to you. NV
PCB Files and
Getting your PCB made
commercially requires that you send
your design via the Internet (there are
a few exceptions). You will need the
following files in “Gerber” format for a
standard double-sided PCB: 1) top
trace layout, 2) bottom trace layout,
3) silkscreen (if used), 4) soldermask
(if used), 5) an aperture file, and 6)
Excellon drill file. The Gerber format
is a standard PCB format that virtually
all layout software supports.
We’ve already discussed items 1
through 4. The Gerber files define the
trace placement, but don’t specify the
physical sizes. The aperture file does
this with a short list of “flash codes.”
Additionally, the Gerber files don’t
specify the actual size of the holes to
be drilled in the PCB. The Excellon
drill file tells the manufacturer where
the holes are and what size they are
supposed to be. Drilling and etching
are two separate procedures. When
you send these files, be sure to add a
short “Read Me” file that relates your
file names to the physical parts of the
PCB. This saves time and confusion.
Circle #147 on the Reader Service Card.
Circle #120 on the Reader Service Card.