58 The PCB Design Magazine • September 2015
by karel Tavernier
uCAMCO
It is clearly possible to fabricate PCBs from
the fabrication data sets currently being used;
it's being done innumerable times every day
all over the globe. But is it being done in an
efficient, reliable, automated and standardized
manner? At this moment in time, the honest
answer is no, because there is plenty of room for
improvement in the way in which PCB fabrica-
tion data is currently transferred from design to
fabrication.
This is not about the Gerber format, which
is used for more than 90% of the world's PCB
production. There are very rarely problems with
Gerber files themselves; they allow images to be
transferred without a hitch. In fact the Gerber
format is part of the solution, given that it is
the most reliable option in this field. The pro-
blems actually lie in which images are transfer-
red, how the format is used and, more often, in
how it is not used.
In this monthly series, Karel Tavernier
explains in detail how to use the newly revised
Gerber data format to communicate with your
fabrication partners clearly and simply, using
an unequivocal yet versatile language that
enables you and them to get the very best out
of your design data. Each month we'll look at a
different aspect of the design to fabrication data
transfer process.
This article has been excerpted from the
Guide to PCB Fabrication Data: Design to Fabri-
cation Data Transfer.
Chapter 2: Alignment (Registration)
Never mirror or flip layers! All layers must
be viewed from the top of the PCB, which me-
ans that the text must be readable on the top
layer and mirrored on the bottom layer. Alas,
sometimes, in a mistaken attempt to be helpful,
designers flip layers because they must anyway
be mirrored on the photoplotter. This could be
helpful in a world where the designer's files are
used directly in fabrication, but these data layers
are actually input for the CAM system. This ne-
eds the correct 2.5D PC structure, so designers
need to follow the standard protocol for provi-
ding digital data. The fabricator's CAM system
article
The Gerber Guide
chapter 2
