EMI Shielding Engineering Handbook EMI Shielding - INSCO Group

EMI Shielding/Grounding Spacer Gaskets continued
Finite Element Analysis
Chomerics, a division of the Parker
Hannifin Corporation’s Seal Group, is
the headquarters of Parker Seal’s
Elastomer Simulation Group. This unit
specializes in elastomer finite element
analysis (FEA) using MARC K6 series
software as a foundation for FEA
capability.
16
Benefits of FEA include:
■ Quickly optimizing elastomer
gasket designs
■ Allowing accurate predictions of
alternate elastomer design concepts
■ Eliminating extensive trial and error
prototype evaluation
Figure 3 FEA Example of an EMI
Spacer Gasket Cross Section
Figure 4 Continuous (top) and Interrupted
Elastomer Gaskets
Typical use of FEA
in EMI spacer gasket
designs is to evaluate
the force vs. deflection
requirements of
alternate designs.
For example, one
spacer design features a
continuous bead of conductive
elastomer molded
onto a plastic spacer. An
alternative design
employs an “interrupted
bead,” where the interruptions
(gaps left on the
plastic frame) are sized to
maintain the required
level of EMI shielding. Figure 4
illustrates these alternative designs.
Gasket Deflection
Figure 5 compares the effect of
continuous and interrupted elastomer
gasket designs in terms of the force
required to deflect the conductive
elastomer. This actual cellular handset
application required a spacer gasket
with interrupted bead to meet desired
deflection forces.
Compression, lbs (kg)
70 (31.75)
60 (27.22)
50 (22.68)
40 (18.14)
30 (13.61)
20 (9.07)
10 (4.54)
0 (0)
0
(0)
0.002
(0.051)
0.004
(0.102)
US Headquarters TEL +(1) 781-935-4850 FAX +(1) 781-933-4318 • www.chomerics.com
Europe TEL +(44) 1628 404000 FAX +(44) 1628 404090
Asia Pacific TEL +(852) 2 428 8008 FAX +(852) 2 423 8253
South America TEL +(55) 11 3917 1099 FAX +(55) 11 3917 0817
Chomerics Design
and Application Services
Chomerics will custom design a
spacer for your application. Advice,
analysis and design assistance will be
provided by Chomerics Applications
and Design engineers at no additional
fee. Contact Chomerics directly
at the locations listed at the bottom of
the page.
Cellular Handset Spacer Gasket
12 inches (30.48 cm) Length
0.006
(0.152)
0.008
(0.203)
0.01
(0.254)
Deflection, inches (mm)
Continuous Gasket
Interrupted Gasket (see Figure 4)
0.012
(0.305)
Figure 5 Typical Spacer Gasket Deflection
0.014
(0.356)
0.016
(0.406)