EoW March 2013

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Technical article
March 2013 87
Abstract
With the number of high performing
dielectric materials available today,
selecting the ideal insulating materials
for high demand cables is a balance
of performance, processability and
cost. This paper will present electrical
performance and selection criteria
for foam fluoropolymer dielectrics.
Establishing viable processing ranges and
key processing considerations, which will
provide a stable, repeatable process, will
also be investigated.
Foam fluoropolymers offer excellent
electrical characteristics, low smoke and
high temperature resistance. Typically
fluoropolymers are used in applications
where low smoke is required such
as plenum cables, high temperature
applications such as military specified
cables and applications requiring
resistance to soldering.
Selecting the right polymer as it relates to
product size and the electrical properties
is important in obtaining a robust process
and desired cable performance. Processing
and monitoring equipment selection and
their operation are important to producing
quality product at high yields. The intent
of this paper is to explain some of these
key product and process characteristics
and their effects on the process and
performance.
Selecting the
right material
Considerations for selecting a foaming
fluoropolymer resin for high performance
cables include electrical/physical perfor-
mance needs, product conductor size
and dielectric wall thickness. Electrical
performance, as the graph below indicates,
can vary with resin composition.
The dissipation factor data (Figure 1)
illustrates differences measured on solid
plaques of various grades of DuPont™
Airquick FFR foam resins in their solid state
(un-foamed).
The attenuation results (Figure 2) are
based upon actual 50-ohm cable samples
produced using identical design and
processing conditions but varying resin
grades.
As illustrated in Figure 2, there can be a
significant difference in the cable loss
based on grade selection.
Foam fluoropolymer
solutions and processing
for insulating high
performance cables
By Gary G Thuot and Robert T Young, of DuPont Chemicals and Fluoroproducts, Wilmington, Delaware, USA
Frequency
Dissipation Factor
Frequency(Ghz)
Attenuation db
▼ ▼ Figure 2: Attenuation
▼ ▼ Figure 1: Dissipation factor