MAY 2022 I PCB007 MAGAZINE 61
need for materials with better and more con-
sistent dielectric properties. His triangular
representation of low-loss materials had FR-4
grades at the base and PTFE at the apex, with
many proprietary products occupying the
intermediate levels. Not just price, but avail-
ability, could influence the choice and again he
stressed the importance of consulting the PCB
supplier before specifying a particular propri-
etary material.
Turning to the characteristics of woven-
glass reinforced materials, he illustrated how
glass weave and resin content could cause local
variations in dielectric constant and hence the
impedance uniformity of embedded conduc-
tors.
He discussed details of component place-
ment and conductor routing, and gave several
examples of good and bad practice in optimis-
ing signal integrity. It was clear that Op den
Camp himself had high-level expertise as a
designer in addition to his knowledge of mate-
rials and fabrication technology. He echoed
Hermann Reischer's comments on the bene-
fits of back-drilling via stubs, and also recom-
mended the removal of non-functional pads on
high-speed vias.
NCAB had a whole series of design rules and
guidelines available for download from their
website, and their applications engineers were
always on hand to answer specific questions.
Having learned the theoretical background
of signal integrity and controlled imped-
ance, complemented by a review of the prac-
tical aspects of the design and manufacture of
printed circuit boards for high-speed applica-
tions, it remained to explore the technology of
ensuring the integrity of the signal as it passed
through interconnecting components. e
final presentation came from a Phoenix Con-
tact specialist in the design and optimisation of
data connectors, Sebastian Stamm.
He began by making it clear that although
signal integrity was a very important consid-
eration, it was one of many product require-
ments. Cost and installation space were fac-
tors that reduced design freedom. erefore
the target was not to achieve signal integrity at
any price, but to produce application-oriented
connectors with high signal integrity.
Sebastian Stamm
