RFi/EMI dual elastomer shielding gasket0 pages

Ultra-Vanshield

®

RFI/EMI dual elastomer shielding gaskets

The challenge for the RFI/EMI industry has been to create a
highly conductive shielding gasket that maintains its mechanical
integrity long-term. Dual Elastomer ULTRA-VANSHIELD® is
definitively the unique solution to this problem.
Each style incorporates design features
not commonly found in other forms of
shielding gaskets. Some of the more
important advantages to consider are:
• Continuously extruded high-strength
silicone rubber core
• Co-extruded highly conductive metalfilled silicone outer layer
• Extremely high shielding effectiveness
• Environmental sealing
• No compression set
• Low compression force
• Extreme environment and abrasionresistant options
• Simple installation options

Silver-filled elastomers have long been used for shielding
against electromagnetic interference and radio frequency signals.
Silver was chosen since it is an excellent conductor and is one of
the few materials that can be put into a rubber matrix while
retaining its conductivity.

patent no. 4,968,854
other patents pending

conductive
outer layer
resilient
elastomeric
inner core

Figure 1. Typical Dual Elastomer gaskets

However, standard silver-filled elastomers
have intrinsic problems. Typically, the
percentage of silver in the elastomer is
extraordinarily high – as much as 70% by
weight. At these concentrations, the elastomer
matrix loses most of its desirable physical
attributes.
The result is neither the desired metallic
nor elastomeric properties, but rather a
compromise between both. For this reason,
conventional silver-filled elastomers have poor
physical properties; i.e. low tear resistance and
tensile strength along with inordinately high
compression forces.

comparison to other designs
ULTRA-VANSHIELD® DUAL ELASTOMERS offer the optimum
combination of metallic conductivity and elastomeric performance.
• Resilient inner core remains free of metal fillers, resulting in
optimum compression and aging properties.
• Silver conductive material is only present in the outer thin
membrane, resulting in excellent conductive properties.
• Thin silver layer permits reduction of costly silver content
required.
• Attenuation performance is not degraded
compression as with solid-filled elastomers.
• Very low compression
resistance to deformation.

force

under

and

• Manufacturing flexibility and quick
turnaround of custom designs. Viable
short run alternative.
• Easy termination. No requirements for
end treatment.

GASKET TYPE
ULTRA-VANSHIELD
Mesh
Filled Elastomers
Beryllium Copper
Clad Foam

full
ATTENUATION
UP TO 1GHz
110dB
60-100dB
90-100dB
100dB
60-80dB

Standard filled elastomers have poor mechanical
properties due to the presence of metal fillers throughout.
Common limitations include very high
COMPRESSION
compression
forces,
undesirable
FORCE SET RANGE
(lbs./in. (% free (% free
compression set, brittleness, poor aging
deflection) height) height)
COST
characteristics and high cost. Some
None 80-90% Moderate
Low
designs lose attenuation properties
High 12-20% 40-60% Moderate
High
High 7-15% 40-60%
beyond 50% compression of relaxed
High
Medium 1-2% 85-90%
height.
Low 15-20% 70-80% Moderate

Table 1. Comparison of common RFI/EMI gasket types

• Available with a variety of optional
conductive metals. See related information on pages 12, 13 and
15.

Other gasket designs, while having certain acceptable
application-specific features, tend to be limited in a general purpose
sense. Specifically, some of the common types lack many of the
intrinsic features necessary for effective long-term shielding.

2

Meshes have very high compression forces and poor
compression set properties along with a limited range of
deflection. Environmental sealing of the tandem designs
increases the compression forces and is often an unsatisfactory
compromise. High frequency performance varies widely.
Terminated ends can allow escape of loose slivers.

Beryllium
copper
gaskets
are
expensive and require even more added
expense for platings to protect from corrosion. In addition, they
lack good environmental sealing options.
Clad foams have low attenuation, a limited range of
compression, poor compression set properties, and designs
are limited due to the manufacturing process and the
conductive materials available for the cladding.